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<div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Software design pattern</div> The memento pattern is a <a href="/wiki/Software_design_pattern" title="Software design pattern">software design pattern</a> that exposes the private internal state of an object. One example of how this can be used is to restore an object to its previous state (undo via rollback), another is versioning, another is custom serialization. The memento pattern is implemented with three objects: the originator, a caretaker and a memento. The originator is some object that has an internal state. The caretaker is going to do something to the originator, but wants to be able to undo the change. The caretaker first asks the originator for a memento object. Then it does whatever operation (or sequence of operations) it was going to do. To roll back to the state before the operations, it returns the memento object to the originator. The memento object itself is an opaque object (one which the caretaker cannot, or should not, change). When using this pattern, care should be taken if the originator may change other objects or resources—the memento pattern operates on a single object. Classic examples of the memento pattern include a <a href="/wiki/Pseudorandom_number_generator" title="Pseudorandom number generator">pseudorandom number generator</a> (each consumer of the PRNG serves as a caretaker who can initialize the PRNG (the originator) with the same seed (the memento) to produce an identical sequence of pseudorandom numbers) and the state in a finite state machine. <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Structure">Structure</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=1" title="Edit section: Structure">edit</a>]</div> <div class="mw-heading mw-heading3"><h3 id="UML_class_and_sequence_diagram">UML class and sequence diagram</h3>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=2" title="Edit section: UML class and sequence diagram">edit</a>]</div> <figure class="mw-halign-none" typeof="mw:File/Frame"><a href="/wiki/File:W3sDesign_Memento_Design_Pattern_UML.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/3/38/W3sDesign_Memento_Design_Pattern_UML.jpg" decoding="async" width="680" height="240" class="mw-file-element" data-file-width="680" data-file-height="240" /></a><figcaption>A sample UML class and sequence diagram for the Memento design pattern.<a href="#cite_note-1">[1]</a></figcaption></figure> In the above UML class diagram, the <code>Caretaker</code> class refers to the <code>Originator</code> class for saving (<code>createMemento()</code>) and restoring (<code>restore(memento)</code>) originator's internal state. The <code>Originator</code> class implements (1) <code>createMemento()</code> by creating and returning a <code>Memento</code> object that stores originator's current internal state and (2) <code>restore(memento)</code> by restoring state from the passed in <code>Memento</code> object. The <a href="/wiki/Unified_Modeling_Language" title="Unified Modeling Language">UML</a> sequence diagram shows the run-time interactions: (1) Saving originator's internal state: The <code>Caretaker</code> object calls <code>createMemento()</code> on the <code>Originator</code> object, which creates a <code>Memento</code> object, saves its current internal state (<code>setState()</code>), and returns the <code>Memento</code> to the <code>Caretaker</code>. (2) Restoring originator's internal state: The <code>Caretaker</code> calls <code>restore(memento)</code> on the <code>Originator</code> object and specifies the <code>Memento</code> object that stores the state that should be restored. The <code>Originator</code> gets the state (<code>getState()</code>) from the <code>Memento</code> to set its own state. <div class="mw-heading mw-heading2"><h2 id="Java_example">Java example</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=3" title="Edit section: Java example">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><a href="/wiki/File:Wikibooks-logo-en-noslogan.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/40px-Wikibooks-logo-en-noslogan.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/60px-Wikibooks-logo-en-noslogan.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/80px-Wikibooks-logo-en-noslogan.svg.png 2x" data-file-width="400" data-file-height="400" /></a></div> <div class="side-box-text plainlist">The Wikibook <a href="https://en.wikibooks.org/wiki/Computer_Science_Design_Patterns" class="extiw" title="wikibooks:Computer Science Design Patterns">Computer Science Design Patterns</a> has a page on the topic of: <a href="https://en.wikibooks.org/wiki/Computer_Science_Design_Patterns/Memento" class="extiw" title="wikibooks:Computer Science Design Patterns/Memento">Memento implementations in various languages</a></div></div> </div> The following Java program illustrates the "undo" usage of the memento pattern. <div class="mw-highlight mw-highlight-lang-java mw-content-ltr" dir="ltr"><pre>import java.util.List; import java.util.ArrayList; class Originator { private String state; // The class could also contain additional data that is not part of the // state saved in the memento.. public void set(String state) { this.state = state; System.out.println("Originator: Setting state to " + state); } public Memento saveToMemento() { System.out.println("Originator: Saving to Memento."); return new Memento(this.state); } public void restoreFromMemento(Memento memento) { this.state = memento.getSavedState(); System.out.println("Originator: State after restoring from Memento: " + state); } public static class Memento { private final String state; public Memento(String stateToSave) { state = stateToSave; } // accessible by outer class only private String getSavedState() { return state; } } } class Caretaker { public static void main(String[] args) { List<Originator.Memento> savedStates = new ArrayList<Originator.Memento>(); Originator originator = new Originator(); originator.set("State1"); originator.set("State2"); savedStates.add(originator.saveToMemento()); originator.set("State3"); // We can request multiple mementos, and choose which one to roll back to. savedStates.add(originator.saveToMemento()); originator.set("State4"); originator.restoreFromMemento(savedStates.get(1)); } } </pre></div> The output is: <pre>Originator: Setting state to State1 Originator: Setting state to State2 Originator: Saving to Memento. Originator: Setting state to State3 Originator: Saving to Memento. Originator: Setting state to State4 Originator: State after restoring from Memento: State3 </pre> This example uses a String as the state, which is an immutable object in Java. In real-life scenarios the state will almost always be a mutable object, in which case a copy of the state must be made. It must be said that the implementation shown has a drawback: it declares an internal class. It would be better if this memento strategy could apply to more than one originator. There are mainly three other ways to achieve Memento: <ol><li>Serialization.</li> <li>A class declared in the same package.</li> <li>The object can also be accessed via a proxy, which can achieve any save/restore operation on the object.</li></ol> <div class="mw-heading mw-heading2"><h2 id="C#_example">C# example</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=4" title="Edit section: C# example">edit</a>]</div> The memento pattern allows one to capture the internal state of an object without violating encapsulation such that later one can undo/revert the changes if required. Here one can see that the memento object is actually used to revert the changes made in the object. <div class="mw-highlight mw-highlight-lang-csharp mw-content-ltr" dir="ltr"><pre>class Memento { private readonly string savedState; private Memento(string stateToSave) { savedState = stateToSave; } public class Originator { private string state; // The class could also contain additional data that is not part of the // state saved in the memento. public void Set(string state) { Console.WriteLine("Originator: Setting state to " + state); this.state = state; } public Memento SaveToMemento() { Console.WriteLine("Originator: Saving to Memento."); return new Memento(state); } public void RestoreFromMemento(Memento memento) { state = memento.savedState; Console.WriteLine("Originator: State after restoring from Memento: " + state); } } } class Caretaker { static void Main(string[] args) { var savedStates = new List<Memento>(); var originator = new Memento.Originator(); originator.Set("State1"); originator.Set("State2"); savedStates.Add(originator.SaveToMemento()); originator.Set("State3"); // We can request multiple mementos, and choose which one to roll back to. savedStates.Add(originator.SaveToMemento()); originator.Set("State4"); originator.RestoreFromMemento(savedStates[1]); } } </pre></div> <div class="mw-heading mw-heading2"><h2 id="Python_example">Python example</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=5" title="Edit section: Python example">edit</a>]</div> <div class="mw-highlight mw-highlight-lang-python mw-content-ltr" dir="ltr"><pre>""" Memento pattern example. """ class Originator: _state = "" def set(self, state: str) -> None: print(f"Originator: Setting state to {state}") self._state = state def save_to_memento(self) -> "Memento": return self.Memento(self._state) def restore_from_memento(self, m: "Memento") -> None: self._state = m.get_saved_state() print(f"Originator: State after restoring from Memento: {self._state}") class Memento: def __init__(self, state): self._state = state def get_saved_state(self): return self._state saved_states = [] originator = Originator() originator.set("State1") originator.set("State2") saved_states.append(originator.save_to_memento()) originator.set("State3") saved_states.append(originator.save_to_memento()) originator.set("State4") originator.restore_from_memento(saved_states[1]) </pre></div> <div class="mw-heading mw-heading2"><h2 id="Javascript_example">Javascript example</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=6" title="Edit section: Javascript example">edit</a>]</div> <div class="mw-highlight mw-highlight-lang-javascript mw-content-ltr" dir="ltr"><pre>// The Memento pattern is used to save and restore the state of an object. // A memento is a snapshot of an object's state. var Memento = {// Namespace: Memento savedState : null, // The saved state of the object. save : function(state) { // Save the state of an object. this.savedState = state; }, restore : function() { // Restore the state of an object. return this.savedState; } }; // The Originator is the object that creates the memento. // defines a method for saving the state inside a memento. var Originator = {// Namespace: Originator state : null, // The state to be stored // Creates a new originator with an initial state of null createMemento : function() { return { state : this.state // The state is copied to the memento. }; }, setMemento : function(memento) { // Sets the state of the originator from a memento this.state = memento.state; } }; // The Caretaker stores mementos of the objects and // provides operations to retrieve them. var Caretaker = {// Namespace: Caretaker mementos : [], // The mementos of the objects. addMemento : function(memento) { // Add a memento to the collection. this.mementos.push(memento); }, getMemento : function(index) { // Get a memento from the collection. return this.mementos[index]; } }; var action_step = "Foo"; // The action to be executed/the object state to be stored. var action_step_2 = "Bar"; // The action to be executed/the object state to be stored. // set the initial state Originator.state = action_step; Caretaker.addMemento(Originator.createMemento());// save the state to the history console.log("Initial State: " + Originator.state); // Foo // change the state Originator.state = action_step_2; Caretaker.addMemento(Originator.createMemento()); // save the state to the history console.log("State After Change: " + Originator.state); // Bar // restore the first state - undo Originator.setMemento(Caretaker.getMemento(0)); console.log("State After Undo: " + Originator.state); // Foo // restore the second state - redo Originator.setMemento(Caretaker.getMemento(1)); console.log("State After Redo: " + Originator.state); // Bar </pre></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=7" title="Edit section: References">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><a href="#cite_ref-1">^</a> <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://w3sdesign.com/?gr=b06&ugr=struct">"The Memento design pattern - Structure and Collaboration"</a>. w3sDesign.com. Retrieved 2017-08-12.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=w3sDesign.com&rft.atitle=The+Memento+design+pattern+-+Structure+and+Collaboration&rft_id=http%3A%2F%2Fw3sdesign.com%2F%3Fgr%3Db06%26ugr%3Dstruct&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMemento+pattern" class="Z3988"> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2>[<a href="/w/index.php?title=Memento_pattern&action=edit&section=8" title="Edit section: External links">edit</a>]</div> <ul><li>Description of Memento Pattern in Ada</li> <li>Memento UML Class Diagram with C# and .NET code samples</li> <li>SourceMaking Tutorial</li> <li>Memento Design Pattern using Java</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist 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style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Creational_pattern" title="Creational pattern">Creational</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abstract_factory_pattern" title="Abstract factory pattern">Abstract factory</a></li> <li><a href="/wiki/Builder_pattern" title="Builder pattern">Builder</a></li> <li><a href="/wiki/Factory_method_pattern" title="Factory method pattern">Factory method</a></li> <li><a href="/wiki/Prototype_pattern" title="Prototype pattern">Prototype</a></li> <li><a href="/wiki/Singleton_pattern" title="Singleton pattern">Singleton</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Structural_pattern" title="Structural pattern">Structural</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div 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class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Active_object" title="Active object">Active object</a></li> <li><a href="/wiki/Balking_pattern" title="Balking pattern">Balking</a></li> <li><a href="/wiki/Binding_properties_pattern" title="Binding properties pattern">Binding properties</a></li> <li><a href="/wiki/Double-checked_locking" title="Double-checked locking">Double-checked locking</a></li> <li><a href="/wiki/Asynchronous_method_invocation" title="Asynchronous method invocation">Event-based asynchronous</a></li> <li><a href="/wiki/Guarded_suspension" title="Guarded suspension">Guarded suspension</a></li> <li><a href="/wiki/Join-pattern" title="Join-pattern">Join</a></li> <li><a href="/wiki/Lock_(computer_science)" title="Lock (computer science)">Lock</a></li> <li><a href="/wiki/Monitor_(synchronization)" title="Monitor (synchronization)">Monitor</a></li> <li><a href="/wiki/Proactor_pattern" title="Proactor pattern">Proactor</a></li> <li><a href="/wiki/Reactor_pattern" title="Reactor pattern">Reactor</a></li> <li><a href="/wiki/Readers%E2%80%93writer_lock" title="Readers–writer lock">Read–write lock</a></li> <li><a href="/wiki/Scheduler_pattern" class="mw-redirect" title="Scheduler pattern">Scheduler</a></li> <li><a href="/wiki/Scheduled-task_pattern" title="Scheduled-task pattern">Scheduled-task pattern</a></li> <li><a href="/wiki/Semaphore_(programming)" title="Semaphore (programming)">Semaphore</a></li> <li><a href="/wiki/Thread_pool" title="Thread pool">Thread pool</a></li> <li><a href="/wiki/Thread-local_storage" title="Thread-local storage">Thread-local storage</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Architectural_pattern" title="Architectural pattern">Architectural patterns</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Front_controller" title="Front controller">Front controller</a></li> <li><a href="/wiki/Interceptor_pattern" title="Interceptor pattern">Interceptor</a></li> <li><a href="/wiki/Model%E2%80%93view%E2%80%93controller" title="Model–view–controller">MVC</a> <ul><li><a href="/wiki/Model%E2%80%93view%E2%80%93presenter" title="Model–view–presenter">MVP</a></li> <li><a href="/wiki/Model%E2%80%93view%E2%80%93viewmodel" title="Model–view–viewmodel">MVVM</a></li></ul></li> <li><a href="/wiki/Action%E2%80%93domain%E2%80%93responder" title="Action–domain–responder">ADR</a></li> <li><a href="/wiki/Entity_component_system" title="Entity component system">ECS</a></li> <li><a href="/wiki/Multitier_architecture" title="Multitier architecture">n-tier</a></li> <li><a href="/wiki/Specification_pattern" title="Specification pattern">Specification</a></li> <li><a href="/wiki/Publish%E2%80%93subscribe_pattern" title="Publish–subscribe pattern">Publish–subscribe</a></li> <li><a href="/wiki/Naked_objects" title="Naked objects">Naked objects</a></li> <li><a href="/wiki/Service_locator_pattern" title="Service locator pattern">Service locator</a></li> <li><a href="/wiki/Active_record_pattern" title="Active record pattern">Active record</a></li> <li><a href="/wiki/Identity_map_pattern" title="Identity map pattern">Identity map</a></li> <li><a href="/wiki/Data_access_object" title="Data access object">Data access object</a></li> <li><a href="/wiki/Data_transfer_object" title="Data transfer object">Data transfer object</a></li> <li><a href="/wiki/Inversion_of_control" title="Inversion of control">Inversion of control</a></li> <li><a href="/wiki/JSP_model_2_architecture" title="JSP model 2 architecture">Model 2</a></li> <li><a href="/wiki/Broker_pattern" title="Broker pattern">Broker</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other patterns</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Blackboard_design_pattern" class="mw-redirect" title="Blackboard design pattern">Blackboard</a></li> <li><a href="/wiki/Business_delegate_pattern" title="Business delegate pattern">Business delegate</a></li> <li><a href="/wiki/Composite_entity_pattern" title="Composite entity pattern">Composite entity</a></li> <li><a href="/wiki/Dependency_injection" title="Dependency injection">Dependency injection</a></li> <li><a href="/wiki/Intercepting_filter_pattern" title="Intercepting filter pattern">Intercepting filter</a></li> <li><a href="/wiki/Lazy_loading" title="Lazy loading">Lazy loading</a></li> <li><a href="/wiki/Mock_object" title="Mock object">Mock object</a></li> <li><a href="/wiki/Null_object_pattern" title="Null object pattern">Null object</a></li> <li><a href="/wiki/Object_pool_pattern" title="Object pool pattern">Object pool</a></li> <li><a href="/wiki/Servant_(design_pattern)" title="Servant (design pattern)">Servant</a></li> <li><a href="/wiki/Twin_pattern" title="Twin pattern">Twin</a></li> <li><a href="/wiki/Type_Tunnel_pattern" class="mw-redirect" title="Type Tunnel pattern">Type tunnel</a></li> <li><a href="/wiki/Method_chaining" title="Method chaining">Method chaining</a></li> <li><a href="/wiki/Delegation_pattern" title="Delegation pattern">Delegation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Books</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Design_Patterns" title="Design Patterns">Design Patterns</a></li> <li><a href="/wiki/Enterprise_Integration_Patterns" title="Enterprise Integration Patterns">Enterprise Integration Patterns</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">People</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Christopher_Alexander" title="Christopher Alexander">Christopher Alexander</a></li> <li><a href="/wiki/Erich_Gamma" title="Erich Gamma">Erich Gamma</a></li> <li><a href="/wiki/Ralph_Johnson_(computer_scientist)" title="Ralph Johnson (computer scientist)">Ralph Johnson</a></li> <li><a href="/wiki/John_Vlissides" title="John Vlissides">John Vlissides</a></li> <li><a href="/wiki/Grady_Booch" title="Grady Booch">Grady Booch</a></li> <li><a href="/wiki/Kent_Beck" title="Kent Beck">Kent Beck</a></li> <li><a href="/wiki/Ward_Cunningham" title="Ward Cunningham">Ward Cunningham</a></li> <li><a href="/wiki/Martin_Fowler_(software_engineer)" title="Martin Fowler (software engineer)">Martin Fowler</a></li> <li><a href="/wiki/Robert_C._Martin" title="Robert C. Martin">Robert Martin</a></li> <li><a href="/wiki/Jim_Coplien" title="Jim Coplien">Jim Coplien</a></li> <li><a href="/wiki/Douglas_C._Schmidt" title="Douglas C. Schmidt">Douglas Schmidt</a></li> <li><a href="/wiki/Linda_Rising" title="Linda Rising">Linda Rising</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Communities</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/The_Hillside_Group" title="The Hillside Group">The Hillside Group</a></li> <li><a href="/wiki/Portland_Pattern_Repository" title="Portland Pattern Repository">Portland Pattern Repository</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">See also</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Anti-pattern" title="Anti-pattern">Anti-pattern</a></li> <li><a href="/wiki/Architectural_pattern" title="Architectural pattern">Architectural pattern</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Memento_pattern&oldid=1243079109">https://en.wikipedia.org/w/index.php?title=Memento_pattern&oldid=1243079109</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Category</a>: <ul><li><a href="/wiki/Category:Software_design_patterns" title="Category:Software design patterns">Software design patterns</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li><li><a href="/wiki/Category:Articles_with_example_Java_code" title="Category:Articles with example Java code">Articles with example Java code</a></li><li><a href="/wiki/Category:Articles_with_example_C_Sharp_code" title="Category:Articles with example C Sharp code">Articles with example C Sharp code</a></li><li><a href="/wiki/Category:Articles_with_example_Python_(programming_language)_code" title="Category:Articles with example Python (programming language) code">Articles with example Python (programming language) code</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 30 August 2024, at 11:15 (UTC).</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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