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href="/libraries/dart-convert"><div><span>dart:convert</span></div></a></li><li class="nav-item"><a class="nav-link" href="/libraries/dart-io"><div><span>dart:io</span></div></a></li><li class="nav-item"><a class="nav-link" href="/interop/js-interop"><div><span>dart:js_interop</span></div></a></li><div class="sidenav-divider"></div><li class="nav-item"><a class="nav-link" href="/libraries/collections/iterables"><div><span>Iterable collections</span></div></a></li><li class="nav-item"><button class="nav-link collapsible collapsed" data-toggle="collapse" data-target="#-sidenav-2-10" role="button" aria-expanded="false" aria-controls="-sidenav-2-10"><span>Asynchronous programming</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-2-10"><li class="nav-item"><a class="nav-link" href="/libraries/async/async-await"><div><span>Tutorial</span></div></a></li><li class="nav-item"><a class="nav-link" href="/libraries/async/futures-error-handling"><div><span>Futures and error handling</span></div></a></li><li class="nav-item"><a class="nav-link" href="/libraries/async/using-streams"><div><span>Using streams</span></div></a></li><li class="nav-item"><a class="nav-link" href="/libraries/async/creating-streams"><div><span>Creating streams</span></div></a></li></ul></li></ul></li><li class="nav-item"><button class="nav-link collapsed collapsible" data-toggle="collapse" data-target="#-sidenav-3" role="button" aria-expanded="false" aria-controls="-sidenav-3"><span>Effective Dart</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-3"><li class="nav-item"><a class="nav-link" href="/effective-dart"><div><span>Overview</span></div></a></li><li class="nav-item"><a class="nav-link" href="/effective-dart/style"><div><span>Style</span></div></a></li><li class="nav-item"><a class="nav-link" href="/effective-dart/documentation"><div><span>Documentation</span></div></a></li><li class="nav-item"><a class="nav-link" href="/effective-dart/usage"><div><span>Usage</span></div></a></li><li class="nav-item"><a class="nav-link" href="/effective-dart/design"><div><span>Design</span></div></a></li></ul></li><li class="nav-item"><button class="nav-link collapsed collapsible" data-toggle="collapse" data-target="#-sidenav-4" role="button" aria-expanded="false" aria-controls="-sidenav-4"><span>Packages</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-4"><li class="nav-item"><a class="nav-link" href="/tools/pub/packages"><div><span>How to use packages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/resources/useful-packages"><div><span>Commonly used packages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/create-packages"><div><span>Creating packages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/publishing"><div><span>Publishing packages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/writing-package-pages"><div><span>Writing package pages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/workspaces"><div><span>Workspaces (monorepo support)</span></div></a></li><li class="nav-item"><button class="nav-link collapsible collapsed" data-toggle="collapse" data-target="#-sidenav-4-7" role="button" aria-expanded="false" aria-controls="-sidenav-4-7"><span>Package reference</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-4-7"><li class="nav-item"><a class="nav-link" href="/tools/pub/dependencies"><div><span>Dependencies</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/glossary"><div><span>Glossary</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/package-layout"><div><span>Package layout conventions</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/environment-variables"><div><span>Pub environment variables</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/pubspec"><div><span>Pubspec file</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/troubleshoot"><div><span>Troubleshooting pub</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/verified-publishers"><div><span>Verified publishers</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/security-advisories"><div><span>Security advisories</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/versioning"><div><span>Versioning</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tools/pub/custom-package-repositories"><div><span>Custom package repositories</span></div></a></li></ul></li><li class="nav-item"><a class="nav-link" href="/tools/pub/private-files"><div><span>What not to commit</span></div></a></li></ul></li><li class="nav-item"><button class="nav-link collapsed collapsible" data-toggle="collapse" data-target="#-sidenav-5" role="button" aria-expanded="false" aria-controls="-sidenav-5"><span>Development</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-5"><li class="nav-item"><a class="nav-link" href="/libraries/serialization/json"><div><span>JSON serialization</span></div></a></li><li class="nav-item"><a class="nav-link" href="/resources/language/number-representation"><div><span>Number representation</span></div></a></li><li class="nav-item"><a class="nav-link" href="/resources/google-apis"><div><span>Google APIs</span></div></a></li><li class="nav-item"><a class="nav-link" href="/multiplatform-apps"><div><span>Multi-platform apps</span></div></a></li><li class="nav-item"><button class="nav-link collapsible collapsed" data-toggle="collapse" data-target="#-sidenav-5-5" role="button" aria-expanded="false" aria-controls="-sidenav-5-5"><span>Command-line & server apps</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-5-5"><li class="nav-item"><a class="nav-link" href="/server"><div><span>Overview</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/get-started"><div><span>Get started</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/cmdline"><div><span>Write command-line apps</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/fetch-data"><div><span>Fetch data from the internet</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/httpserver"><div><span>Write HTTP servers</span></div></a></li><li class="nav-item"><a class="nav-link" href="/server/libraries"><div><span>Libraries & packages</span></div></a></li><li class="nav-item"><a class="nav-link" href="/server/google-cloud"><div><span>Google Cloud</span></div></a></li></ul></li><li class="nav-item"><button class="nav-link collapsible collapsed" data-toggle="collapse" data-target="#-sidenav-5-6" role="button" aria-expanded="false" aria-controls="-sidenav-5-6"><span>Web apps</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-5-6"><li class="nav-item"><a class="nav-link" href="/web"><div><span>Overview</span></div></a></li><li class="nav-item"><a class="nav-link" href="/web/get-started"><div><span>Get started</span></div></a></li><li class="nav-item"><a class="nav-link" href="/web/deployment"><div><span>Deployment</span></div></a></li><li class="nav-item"><a class="nav-link" href="/web/libraries"><div><span>Libraries & 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class="site-toc__title">Contents</header><ul class="section-nav"><li class="toc-entry nav-item"><a class="nav-link" href="#numbers">Numbers</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#strings">Strings</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#booleans">Booleans</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#runes-and-grapheme-clusters">Runes and grapheme clusters</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#symbols">Symbols</a></li></ul></div><article><div class="content"><div id="site-content-title"><h1>Built-in types</h1></div><div id="site-toc--inline" class="site-toc"><header class="site-toc__title">Contents</header><ul class="section-nav"><li class="toc-entry"><a href="#numbers">Numbers</a></li><li class="toc-entry"><a href="#strings">Strings</a></li><li class="toc-entry"><a href="#booleans">Booleans</a></li><li class="toc-entry"><a href="#runes-and-grapheme-clusters">Runes and grapheme clusters</a></li><li class="toc-entry"><a href="#symbols">Symbols</a></li></ul></div><p>The Dart language has special support for the following:</p><ul><li><a href="#numbers">Numbers</a> (<code>int</code>, <code>double</code>)</li><li><a href="#strings">Strings</a> (<code>String</code>)</li><li><a href="#booleans">Booleans</a> (<code>bool</code>)</li><li><a href="/language/records">Records</a> (<code>(value1, value2)</code>)</li><li><a href="/language/functions#function-types">Functions</a> (<code>Function</code>)</li><li><a href="/language/collections#lists">Lists</a> (<code>List</code>, also known as <em>arrays</em>)</li><li><a href="/language/collections#sets">Sets</a> (<code>Set</code>)</li><li><a href="/language/collections#maps">Maps</a> (<code>Map</code>)</li><li><a href="#runes-and-grapheme-clusters">Runes</a> (<code>Runes</code>; often replaced by the <code>characters</code> API)</li><li><a href="#symbols">Symbols</a> (<code>Symbol</code>)</li><li>The value <code>null</code> (<code>Null</code>)</li></ul><p>This support includes the ability to create objects using literals. For example, <code>'this is a string'</code> is a string literal, and <code>true</code> is a boolean literal.</p><p>Because every variable in Dart refers to an object—an instance of a <em>class</em>—you can usually use <em>constructors</em> to initialize variables. Some of the built-in types have their own constructors. For example, you can use the <code>Map()</code> constructor to create a map.</p><p>Some other types also have special roles in the Dart language:</p><ul><li><code>Object</code>: The superclass of all Dart classes except <code>Null</code>.</li><li><code>Enum</code>: The superclass of all enums.</li><li><code>Future</code> and <code>Stream</code>: Used in <a href="/language/async">asynchrony support</a>.</li><li><code>Iterable</code>: Used in <a href="/libraries/dart-core#iteration">for-in loops</a> and in synchronous <a href="/language/functions#generators">generator functions</a>.</li><li><code>Never</code>: Indicates that an expression can never successfully finish evaluating. Most often used for functions that always throw an exception.</li><li><code>dynamic</code>: Indicates that you want to disable static checking. Usually you should use <code>Object</code> or <code>Object?</code> instead.</li><li><code>void</code>: Indicates that a value is never used. Often used as a return type.</li></ul><p>The <code>Object</code>, <code>Object?</code>, <code>Null</code>, and <code>Never</code> classes have special roles in the class hierarchy. Learn about these roles in <a href="/null-safety/understanding-null-safety#top-and-bottom">Understanding null safety</a>.</p><div class="header-wrapper"><h2 id="numbers">Numbers</h2><a class="heading-link" href="#numbers" aria-label="Link to 'Numbers' section">#</a></div><p>Dart numbers come in two flavors:</p><dl><dt><a href="https://api.dart.dev/dart-core/int-class.html"><code>int</code></a></dt><dd>Integer values no larger than 64 bits, <a href="/resources/language/number-representation">depending on the platform</a>. On native platforms, values can be from -2<sup>63</sup> to 2<sup>63</sup> - 1. On the web, integer values are represented as JavaScript numbers (64-bit floating-point values with no fractional part) and can be from -2<sup>53</sup> to 2<sup>53</sup> - 1.</dd><dt><a href="https://api.dart.dev/dart-core/double-class.html"><code>double</code></a></dt><dd>64-bit (double-precision) floating-point numbers, as specified by the IEEE 754 standard.</dd></dl><p>Both <code>int</code> and <code>double</code> are subtypes of <a href="https://api.dart.dev/dart-core/num-class.html"><code>num</code></a>. The num type includes basic operators such as +, -, /, and *, and is also where you'll find <code>abs()</code>,<code>ceil()</code>, and <code>floor()</code>, among other methods. (Bitwise operators, such as >>, are defined in the <code>int</code> class.) If num and its subtypes don't have what you're looking for, the <a href="https://api.dart.dev/dart-math/dart-math-library.html"><code>dart:math</code></a> library might.</p><p>Integers are numbers without a decimal point. Here are some examples of defining integer literals:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (integer-literals)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> x = </span><span style="color:#11796D">1</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> hex = </span><span style="color:#11796D">0xDEADBEEF</span><span style="color:#222222">;</span></span></code></pre></div></div><p>If a number includes a decimal, it is a double. Here are some examples of defining double literals:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (double-literals)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> y = </span><span style="color:#11796D">1.1</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> exponents = </span><span style="color:#11796D">1.42e5</span><span style="color:#222222">;</span></span></code></pre></div></div><p>You can also declare a variable as a num. If you do this, the variable can have both integer and double values.</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (declare-num)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#0468D7">num</span><span style="color:#222222"> x = </span><span style="color:#11796D">1</span><span style="color:#222222">; </span><span style="color:#6E6E70">// x can have both int and double values</span></span> <span class="line"><span style="color:#222222">x += </span><span style="color:#11796D">2.5</span><span style="color:#222222">;</span></span></code></pre></div></div><p>Integer literals are automatically converted to doubles when necessary:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (int-to-double)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#0468D7">double</span><span style="color:#222222"> z = </span><span style="color:#11796D">1</span><span style="color:#222222">; </span><span style="color:#6E6E70">// Equivalent to double z = 1.0.</span></span></code></pre></div></div><p>Here's how you turn a string into a number, or vice versa:</p> <?code-excerpt "misc/test/language_tour/built_in_types_test.dart (number-conversion)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#6E6E70">// String -> int</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> one = </span><span style="color:#0468D7">int</span><span style="color:#222222">.</span><span style="color:#6200EE">parse</span><span style="color:#222222">(</span><span style="color:#11796D">'1'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(one == </span><span style="color:#11796D">1</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// String -> double</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> onePointOne = </span><span style="color:#0468D7">double</span><span style="color:#222222">.</span><span style="color:#6200EE">parse</span><span style="color:#222222">(</span><span style="color:#11796D">'1.1'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(onePointOne == </span><span style="color:#11796D">1.1</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// int -> String</span></span> <span class="line"><span style="color:#0468D7">String</span><span style="color:#222222"> oneAsString = </span><span style="color:#11796D">1.</span><span style="color:#6200EE">toString</span><span style="color:#222222">();</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(oneAsString == </span><span style="color:#11796D">'1'</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// double -> String</span></span> <span class="line"><span style="color:#0468D7">String</span><span style="color:#222222"> piAsString = </span><span style="color:#11796D">3.14159</span><span style="color:#222222">.</span><span style="color:#6200EE">toStringAsFixed</span><span style="color:#222222">(</span><span style="color:#11796D">2</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(piAsString == </span><span style="color:#11796D">'3.14'</span><span style="color:#222222">);</span></span></code></pre></div></div><p>The <code>int</code> type specifies the traditional bitwise shift (<code><<</code>, <code>>></code>, <code>>>></code>), complement (<code>~</code>), AND (<code>&</code>), OR (<code>|</code>), and XOR (<code>^</code>) operators, which are useful for manipulating and masking flags in bit fields. For example:</p> <?code-excerpt "misc/test/language_tour/built_in_types_test.dart (bit-shifting)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">((</span><span style="color:#11796D">3</span><span style="color:#222222"> << </span><span style="color:#11796D">1</span><span style="color:#222222">) == </span><span style="color:#11796D">6</span><span style="color:#222222">); </span><span style="color:#6E6E70">// 0011 << 1 == 0110</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">((</span><span style="color:#11796D">3</span><span style="color:#222222"> | </span><span style="color:#11796D">4</span><span style="color:#222222">) == </span><span style="color:#11796D">7</span><span style="color:#222222">); </span><span style="color:#6E6E70">// 0011 | 0100 == 0111</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">((</span><span style="color:#11796D">3</span><span style="color:#222222"> & </span><span style="color:#11796D">4</span><span style="color:#222222">) == </span><span style="color:#11796D">0</span><span style="color:#222222">); </span><span style="color:#6E6E70">// 0011 & 0100 == 0000</span></span></code></pre></div></div><p>For more examples, see the <a href="/language/operators#bitwise-and-shift-operators">bitwise and shift operator</a> section.</p><p>Number literals are compile-time constants. Many arithmetic expressions are also compile-time constants, as long as their operands are compile-time constants that evaluate to numbers.</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (const-num)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> msPerSecond = </span><span style="color:#11796D">1000</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> secondsUntilRetry = </span><span style="color:#11796D">5</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> msUntilRetry = secondsUntilRetry * msPerSecond;</span></span></code></pre></div></div><p>For more information, see <a href="/resources/language/number-representation">Numbers in Dart</a>.</p><p><a id="digit-separators"></a></p><p>You can use one or more underscores (<code>_</code>) as digit separators to make long number literals more readable. Multiple digit separators allow for higher level grouping.</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (digit-separators)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> n1 = </span><span style="color:#11796D">1_000_000</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> n2 = </span><span style="color:#11796D">0.000_000_000_01</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> n3 = </span><span style="color:#11796D">0x00_14_22_01_23_45</span><span style="color:#222222">; </span><span style="color:#6E6E70">// MAC address</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> n4 = </span><span style="color:#11796D">555_123_4567</span><span style="color:#222222">; </span><span style="color:#6E6E70">// US Phone number</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> n5 = </span><span style="color:#11796D">100__000_000__000_000</span><span style="color:#222222">; </span><span style="color:#6E6E70">// one hundred million million!</span></span></code></pre></div></div><aside class="alert alert-info"><div class="alert-header"><span class="material-symbols" aria-hidden="true">merge_type</span> <span>Version note</span></div><div class="alert-content"><p>Using digit separators requires a <a href="/resources/language/evolution#language-versioning">language version</a> of at least 3.6.</p></div></aside><div class="header-wrapper"><h2 id="strings">Strings</h2><a class="heading-link" href="#strings" aria-label="Link to 'Strings' section">#</a></div><p>A Dart string (<code>String</code> object) holds a sequence of UTF-16 code units. You can use either single or double quotes to create a string:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (quoting)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s1 = </span><span style="color:#11796D">'Single quotes work well for string literals.'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s2 = </span><span style="color:#11796D">"Double quotes work just as well."</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s3 = </span><span style="color:#11796D">'It</span><span style="color:#222222">\'</span><span style="color:#11796D">s easy to escape the string delimiter.'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s4 = </span><span style="color:#11796D">"It's even easier to use the other delimiter."</span><span style="color:#222222">;</span></span></code></pre></div></div><p><a id="string-interpolation"></a></p><p>You can put the value of an expression inside a string by using <code>${</code><em><code>expression</code></em><code>}</code>. If the expression is an identifier, you can skip the <code>{}</code>. To get the string corresponding to an object, Dart calls the object's <code>toString()</code> method.</p> <?code-excerpt "misc/test/language_tour/built_in_types_test.dart (string-interpolation)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s = </span><span style="color:#11796D">'string interpolation'</span><span style="color:#222222">;</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(</span></span> <span class="line"><span style="color:#11796D"> 'Dart has </span><span style="color:#11796D">$</span><span style="color:#222222">s</span><span style="color:#11796D">, which is very handy.'</span><span style="color:#222222"> ==</span></span> <span class="line"><span style="color:#11796D"> 'Dart has string interpolation, '</span></span> <span class="line"><span style="color:#11796D"> 'which is very handy.'</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#222222">);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(</span></span> <span class="line"><span style="color:#11796D"> 'That deserves all caps. '</span></span> <span class="line"><span style="color:#11796D"> '</span><span style="color:#11796D">${</span><span style="color:#222222">s</span><span style="color:#11796D">.</span><span style="color:#6200EE">toUpperCase</span><span style="color:#11796D">()}</span><span style="color:#11796D"> is very handy!'</span><span style="color:#222222"> ==</span></span> <span class="line"><span style="color:#11796D"> 'That deserves all caps. '</span></span> <span class="line"><span style="color:#11796D"> 'STRING INTERPOLATION is very handy!'</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#222222">);</span></span></code></pre></div></div><aside class="alert alert-info"><div class="alert-header"><span class="material-symbols" aria-hidden="true">info</span> <span>Note</span></div><div class="alert-content"><p>The <code>==</code> operator tests whether two objects are equivalent. Two strings are equivalent if they contain the same sequence of code units.</p></div></aside><p>You can concatenate strings using adjacent string literals or the <code>+</code> operator:</p> <?code-excerpt "misc/test/language_tour/built_in_types_test.dart (adjacent-string-literals)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s1 =</span></span> <span class="line"><span style="color:#11796D"> 'String '</span></span> <span class="line"><span style="color:#11796D"> 'concatenation'</span></span> <span class="line"><span style="color:#11796D"> " works even over line breaks."</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(</span></span> <span class="line"><span style="color:#222222"> s1 ==</span></span> <span class="line"><span style="color:#11796D"> 'String concatenation works even over '</span></span> <span class="line"><span style="color:#11796D"> 'line breaks.'</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s2 = </span><span style="color:#11796D">'The + operator '</span><span style="color:#222222"> + </span><span style="color:#11796D">'works, as well.'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(s2 == </span><span style="color:#11796D">'The + operator works, as well.'</span><span style="color:#222222">);</span></span></code></pre></div></div><p>To create a multi-line string, use a triple quote with either single or double quotation marks:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (triple-quotes)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s1 = </span><span style="color:#11796D">'''</span></span> <span class="line"><span style="color:#11796D">You can create</span></span> <span class="line"><span style="color:#11796D">multi-line strings like this one.</span></span> <span class="line"><span style="color:#11796D">'''</span><span style="color:#222222">;</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s2 = </span><span style="color:#11796D">"""This is also a</span></span> <span class="line"><span style="color:#11796D">multi-line string."""</span><span style="color:#222222">;</span></span></code></pre></div></div><p>You can create a "raw" string by prefixing it with <code>r</code>:</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (raw-strings)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> s = </span><span style="color:#11796D">r'In a raw string, not even \n gets special treatment.'</span><span style="color:#222222">;</span></span></code></pre></div></div><p>See <a href="#runes-and-grapheme-clusters">Runes and grapheme clusters</a> for details on how to express Unicode characters in a string.</p><p>String literals are compile-time constants, as long as any interpolated expression is a compile-time constant that evaluates to null or a numeric, string, or boolean value.</p> <?code-excerpt "misc/lib/language_tour/built_in_types.dart (string-literals)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#6E6E70">// These work in a const string.</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> aConstNum = </span><span style="color:#11796D">0</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> aConstBool = </span><span style="color:#11796D">true</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> aConstString = </span><span style="color:#11796D">'a constant string'</span><span style="color:#222222">;</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// These do NOT work in a const string.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> aNum = </span><span style="color:#11796D">0</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> aBool = </span><span style="color:#11796D">true</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> aString = </span><span style="color:#11796D">'a string'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> aConstList = [</span><span style="color:#11796D">1</span><span style="color:#222222">, </span><span style="color:#11796D">2</span><span style="color:#222222">, </span><span style="color:#11796D">3</span><span style="color:#222222">];</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">const</span><span style="color:#222222"> validConstString = </span><span style="color:#11796D">'</span><span style="color:#11796D">$</span><span style="color:#222222">aConstNum</span><span style="color:#11796D"> $</span><span style="color:#222222">aConstBool</span><span style="color:#11796D"> $</span><span style="color:#222222">aConstString</span><span style="color:#11796D">'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#6E6E70">// const invalidConstString = '$aNum $aBool $aString $aConstList';</span></span></code></pre></div></div><p>For more information on using strings, check out <a href="/libraries/dart-core#strings-and-regular-expressions">Strings and regular expressions</a>.</p><div class="header-wrapper"><h2 id="booleans">Booleans</h2><a class="heading-link" href="#booleans" aria-label="Link to 'Booleans' section">#</a></div><p>To represent boolean values, Dart has a type named <code>bool</code>. Only two objects have type bool: the boolean literals <code>true</code> and <code>false</code>, which are both compile-time constants.</p><p>Dart's type safety means that you can't use code like <code>if (<em>nonbooleanValue</em>)</code> or <code>assert (<em>nonbooleanValue</em>)</code>. Instead, explicitly check for values, like this:</p> <?code-excerpt "misc/test/language_tour/built_in_types_test.dart (no-truthy)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#6E6E70">// Check for an empty string.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> fullName = </span><span style="color:#11796D">''</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(fullName.isEmpty);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// Check for zero.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> hitPoints = </span><span style="color:#11796D">0</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(hitPoints == </span><span style="color:#11796D">0</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// Check for null.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> unicorn = </span><span style="color:#11796D">null</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(unicorn == </span><span style="color:#11796D">null</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#6E6E70">// Check for NaN.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> iMeantToDoThis = </span><span style="color:#11796D">0</span><span style="color:#222222"> / </span><span style="color:#11796D">0</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(iMeantToDoThis.isNaN);</span></span></code></pre></div></div><div class="header-wrapper"><h2 id="runes-and-grapheme-clusters">Runes and grapheme clusters</h2><a class="heading-link" href="#runes-and-grapheme-clusters" aria-label="Link to 'Runes and grapheme clusters' section">#</a></div><p>In Dart, <a href="https://api.dart.dev/dart-core/Runes-class.html">runes</a> expose the Unicode code points of a string. You can use the <a href="https://pub.dev/packages/characters">characters package</a> to view or manipulate user-perceived characters, also known as <a href="https://unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries">Unicode (extended) grapheme clusters.</a></p><p>Unicode defines a unique numeric value for each letter, digit, and symbol used in all of the world's writing systems. Because a Dart string is a sequence of UTF-16 code units, expressing Unicode code points within a string requires special syntax. The usual way to express a Unicode code point is <code>\uXXXX</code>, where XXXX is a 4-digit hexadecimal value. For example, the heart character (♥) is <code>\u2665</code>. To specify more or less than 4 hex digits, place the value in curly brackets. For example, the laughing emoji (😆) is <code>\u{1f606}</code>.</p><p>If you need to read or write individual Unicode characters, use the <code>characters</code> getter defined on String by the characters package. The returned <a href="https://pub.dev/documentation/characters/latest/characters/Characters-class.html"><code>Characters</code></a> object is the string as a sequence of grapheme clusters. Here's an example of using the characters API:</p> <?code-excerpt "misc/lib/language_tour/characters.dart"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">import</span><span style="color:#11796D"> 'package:characters/characters.dart'</span><span style="color:#222222">;</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">void</span><span style="color:#6200EE"> main</span><span style="color:#222222">() {</span></span> <span class="line"><span style="color:#D43324"> var</span><span style="color:#222222"> hi = </span><span style="color:#11796D">'Hi 🇩🇰'</span><span style="color:#222222">;</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(hi);</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(</span><span style="color:#11796D">'The end of the string: </span><span style="color:#11796D">${</span><span style="color:#222222">hi</span><span style="color:#11796D">.</span><span style="color:#6200EE">substring</span><span style="color:#11796D">(</span><span style="color:#222222">hi</span><span style="color:#11796D">.</span><span style="color:#222222">length</span><span style="color:#11796D"> - 1)}</span><span style="color:#11796D">'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(</span><span style="color:#11796D">'The last character: </span><span style="color:#11796D">${</span><span style="color:#222222">hi</span><span style="color:#11796D">.</span><span style="color:#222222">characters</span><span style="color:#11796D">.</span><span style="color:#222222">last</span><span style="color:#11796D">}</span><span style="color:#11796D">'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#222222">}</span></span></code></pre></div></div><p>The output, depending on your environment, looks something like this:</p><div class="code-block-wrapper language-console"><div class="code-block-body"><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#222222">$ dart run bin/main.dart</span></span> <span class="line"><span style="color:#222222">Hi 🇩🇰</span></span> <span class="line"><span style="color:#222222">The end of the string: ???</span></span> <span class="line"><span style="color:#222222">The last character: 🇩🇰</span></span></code></pre></div></div><p>For details on using the characters package to manipulate strings, see the <a href="https://pub.dev/packages/characters/example">example</a> and <a href="https://pub.dev/documentation/characters">API reference</a> for the characters package.</p><div class="header-wrapper"><h2 id="symbols">Symbols</h2><a class="heading-link" href="#symbols" aria-label="Link to 'Symbols' section">#</a></div><p>A <a href="https://api.dart.dev/dart-core/Symbol-class.html"><code>Symbol</code></a> object represents an operator or identifier declared in a Dart program. You might never need to use symbols, but they're invaluable for APIs that refer to identifiers by name, because minification changes identifier names but not identifier symbols.</p><p>To get the symbol for an identifier, use a symbol literal, which is just <code>#</code> followed by the identifier:</p><div class="code-block-wrapper language-plaintext"><div class="code-block-body"><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span>#radix</span></span> <span class="line"><span>#bar</span></span></code></pre></div></div><p>Symbol literals are compile-time constants.</p><nav id="prev-next"><ul><li class="previous"><a href="/language/keywords">&lang;  Keywords</a></li><li class="next"><a href="/language/records">Records  &rang;</a></li></ul></nav><p id="page-github-links"><span>Unless stated otherwise, the documentation on this site reflects Dart 3.7.1. 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