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Topic: Command pattern

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	design:the_command_pattern [phpPatterns]
		The Gang of Four description of the Command Pattern’s intent is “Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.”.
		An alternative way to think about the Command Pattern, from the perspective of PHP (as a language that supports both procedural and object oriented paradigms) might be “To allow multiple implementations of the same function name, each implementation being wrapped in it’s own class”.
		Where the Command Pattern typically turns up in web applications is in frameworks like Struts: the Action class and it’s execute() method.
	www.phppatterns.com /docs/design/the_command_pattern (846 words)

	Command pattern - Wikipedia, the free encyclopedia
		In object-oriented programming, the Command pattern is a design pattern in which objects are used to represent actions.
		A command object can hold information about the command, such as its name or which user launched it; and answer questions about it, such as how long it will likely take.
		The command is a useful abstraction for building generic components, such as a thread pool, that can handle command objects of any type.
	en.wikipedia.org /wiki/Command_pattern (1037 words)

	SENG 443 - Command Design Pattern Web Notes
		The Command pattern is used to encapsulate requests as an object, thus allowing for parameterization of clients with different requests, queues or log requests, and also support for undoable operations (Gamma et al., 1995).
		The Command pattern is different in that it focuses mainly on binding between a receiver and a function, instead of just maintaining the function (Gamma et al., 1995).
		Disadvantages of the command pattern are that it raises the possibility of having too many subclasses and the problem of either having a too intelligent or not intelligent enough command class.
	sern.ucalgary.ca /courses/seng/443/f2004/patternNotes/Collier_Fernandes_&_Hasiuk/index.html (2406 words)

	Distributed Command Pattern - an extension of command pattern for connected systems - The Code Project - Design and ...
		Command Pattern also forces design of a very reusable system because the small command classes are reusable by design and can be invoked either by the user or by any system.
		Whenever a command is sent to the Command Bus, it informs all executors in the pipeline to execute the command.
		As a result, when a command is executed on the bus, the command is sent to the distributed executor and the executor sends the command to the transporter which in turn transmits the message using the Socket it has created.
	www.codeproject.com /cs/design/distributedcommandpattern.asp (3555 words)

	Command Pattern (Site not responding. Last check: 2007-09-19)
		For the other command, such as plotting one part of the spreadsheet is not necessary to undo or redo.
		The leftmost command was issued first, followed by the second-leftmost, and so on until the most recently issued command, which is rightmost.
		Commands to the right of the present line are commands that may be redone in the future.
	www.cs.mcgill.ca /~hv/classes/CS400/01.hchen/doc/command/command.html (821 words)

	sed Command (Site not responding. Last check: 2007-09-19)
		The sed command uses two work spaces for holding the line being modified: the pattern space, where the selected line is held; and the hold space, where a line can be stored temporarily.
		When a command includes an address (either a line number or a search pattern), only the addressed line or lines are affected by the command.
		A command line with two addresses separated by commas selects the entire range from the first line that matches the first address through the next line that matches the second.
	www.unet.univie.ac.at /aix/cmds/aixcmds5/sed.htm (1781 words)

	Command Pattern (Site not responding. Last check: 2007-09-19)
		Commands are parameterized by the variable to be written, word to delete, place to move a figure to, etc. These parameters should be abstract, to avoid embedded references which would hinder logging and communicating a Command.
		Commands are sent to a Command Processor which may queue, prioritize, and distribute them among machines or threads.
		Commands can encapsulate their own undo procedure, or the log can be replayed to simulate undo.
	research.microsoft.com /~minka/patterns/Command.html (1029 words)

	Command
		Command objects can be thought of as "tokens" that are created by one client that knows what need to be done, and passed to another client that has the resources for doing it.
		Command and Memento act as magic tokens to be passed around and invoked at a later time.
		Two important aspects of the Command pattern: interface separation (the invoker is isolated from the receiver), time separation (stores a ready-to-go processing request that's to be stated later).
	home.earthlink.net /~huston2/dp/command.html (773 words)

	Humdrum Toolkit Command Reference -- pattern
		The pattern command is used to locate all occurrences of a user-defined pattern in some Humdrum input.
		In the pattern command, the regular expression counting metacharacters may also be used to specify the number of successive records that match the regular expression.
		Pattern searches may be made sensitive to occurrences of comments (defined in the template) by specifying the -c option.
	www.music-cog.ohio-state.edu /Humdrum/commands/pattern.html (961 words)

	Web services programming tips and tricks: Learn simple, practical Web services design patterns, Part 2
		The command pattern is distinguished by the encapsulation of distinct activities into reusable objects whose behavior can be parameterized per request.
		The assignment of parameters to stateful commands occurs either when the object instance is created or immediately prior to command invocation through the setting of attributes.
		The goal of the pattern is to achieve the same kind of business logic encapsulation achieved by the command pattern while presenting a less complicated, more user-friendly interface to potential clients.
	www-106.ibm.com /developerworks/webservices/library/ws-tip-altdesign2 (1515 words)

	Web services programming tips and tricks: Learn simple, practical Web services design patterns, Part 2
		The command pattern is distinguished by the encapsulation of distinct activities into reusable objects whose behavior can be parameterized per request.
		The assignment of parameters to stateful commands occurs either when the object instance is created or immediately prior to command invocation through the setting of attributes.
		The goal of the pattern is to achieve the same kind of business logic encapsulation achieved by the command pattern while presenting a less complicated, more user-friendly interface to potential clients.
	www-128.ibm.com /developerworks/webservices/library/ws-tip-altdesign2 (1515 words)

	Command - Wikipedia, the free encyclopedia
		In organizations, an office, position of authority or group of people and material under the authority of a single person.
		Command pattern, a design pattern in computer science
		Command key, a modifier key on Apple Macintosh computer keyboards
	en.wikipedia.org /wiki/Command (135 words)

	The Local/Dispatchable Command Pattern (Site not responding. Last check: 2007-09-19)
		The Local/Dispatchable Command Pattern proposes that instead of a single command interface, two are provided - a local command, which will always be executed in the same context as the controller, and a dispatchable command, which has the ability to be transferred to an EJB server for execution.
		The Local/Dispatchable Command Pattern proposes enhancements to the EJB Command Pattern: The commands are provided with access to their environment such as session data, references to application components they require.
		The Local/Dispatchable Command Pattern is not concerned with which type of command to use in a given situation but rather with allowing the developer to decide which execution context best suits their needs.
	www.theserverside.com /patterns/thread.tss?thread_id=14084 (1224 words)

	[No title]
		The receiver is a ReportEngine object, which is created by the command in the Execute function and is passed the report ID to render from the command internal state.
		Commands are implemented as classes that encapsulate requests, as we've seen.
		The primary goal of queuing commands is to invoke the command on a different server than the client, although it could just be a separate process or application domain on the same server.
	msdn.microsoft.com /msdnmag/issues/04/09/CommandPattern (4218 words)

	Design Pattern Summary: Command (Site not responding. Last check: 2007-09-19)
		This pattern is applicable in cases where one would want to configure objects by an action to perform.
		As such, the Command pattern can also provide a mechanism for logging changes as the changes can be reapplied or captured in case of a system crash.
		The Command pattern provides the facilities to encapsulate an operation thereby decoupling the invoker from the receiver.
	pages.cpsc.ucalgary.ca /~phong/courses/SENG609.04/Command.htm (432 words)

	Dr. Dobb's \| Java ME and the Command Pattern \| January 10, 2007
		The more commands you add, the longer the if-else chain grows—and if you want to use the same command on another screen or canvas, you have to copy-and-paste code, which is difficult to maintain.
		The essence of the Command Pattern is to divide the part where the command is implemented from the part where it is invoked (using a predefined interface, of course; this is object orientation after all).
		It extends Command and is an abstract class that defines the interface (not the Java Interface) that all commands have to use by extending AbstractCommand.
	www.ddj.com /dept/java/196802806 (984 words)

	XML.com: Design Patterns in XML Applications
		Command is a behavioral pattern used to encapsulate actions in objects.
		The solution that the command pattern proposes is to encapsulate the changes to the DOM into objects, command objects, each capable of doing (and undoing) a particular action.
		The collection of command objects will be managed by a certain command manager, capable of holding the queue of executed commands, so the user may undo/redo them.
	www.xml.com /pub/a/2000/01/19/feature/index.html?page=2 (684 words)

	SENG 609.04 Design Patterns: Graduate Course
		The Command pattern, which is also known as Action or Transaction, "encapsulates a request as an object, thereby letting you parameterize clients with different request, queue or log request, and support undoable operations " (Gamma et al 1995, p.
		Before a Command object is executed, a copy of the Command object is produced and put into the history list so that the user may choose to undo or redo this Command object later.
		The Command Module of Knowledge Science Institute in the University of Calgary is used as a reference during the implementation of this class library.
	sern.ucalgary.ca /courses/SENG/609.04/W98/jyzhu/classcommand.html (2128 words)

	Control GUI Action in VB6 Using the Command Behavior Pattern
		Each ball command is placed in a stack permitting you to undo the ball movement or rewind all of the movements.
		ProcessCommand is defined to assign a reference to Form1 to the command's Form property, to execute the command, and then to push the command on the collection-cum-stack.
		The Form is dependent on commands because that is how the Form's behaviors are invoked, and the Form has an aggregate relationship with the collection because the Form is responsible for the life of the collection.
	www.devx.com /vb/Article/22610/1954?pf=true (1600 words)

	Living .NET... : Patterns in .NET: Citing the Command Pattern (Site not responding. Last check: 2007-09-19)
		Though design patterns are not restricted to the seminal work from the GOF, they do provide a solid basis on how patterns, in general are conceived.
		Essentially, in this pattern, you encapsulate the command/operation to be executed as an object, with the method parameters represented by the state of command object.
		Therefore, the state of our Command object would contain a delegate instance and an object array, which is passed to the DynamicInvoke method and also, optionally, a result object.
	msmvps.com /blogs/manoj/archive/2005/04/01/40491.aspx (492 words)

	CIOL IT Unlimited
		Commands are parameterized by the variable to be written, word to delete, place to move a figure to, etc. These parameters should be abstract, to avoid embedded references which would hinder logging and communicating a Command.
		Commands are sent to a Command Processor, which may queue, prioritize, and distribute them among machines or threads.
		Commands can encapsulate their own undo procedure, or the log can be replayed to simulate undo.
	www.ciol.com /archive/articledetail.asp?arid=27059 (1456 words)

	Design Patterns: Command Pattern - The Code Project - Book Chapters
		The invoker component acts as a link between the commands and the receiver, and houses the receiver and the individual commands as they are sent.
		The command is an object that encapsulates a request to the receiver.
		The Command pattern keeps a record of changes to an object's state, and applies those changes in an ad-hoc fashion.
	www.codeproject.com /books/DesignPatterns.asp (1515 words)

	[No title]
		The issuer sends the command to the command object by executing a specific method on it.
		The command object is then responsible for dispatching the command to a specific recipient to get the job done.
		This command is translated into a specific action on a specific receiver by the various concrete command objects.
	www.exciton.cs.rice.edu /JavaResources/DesignPatterns/command.htm (228 words)

	Command Pattern
		Command objects manage the processing that occurs when a user manipulates the application in some way.
		You put the command on a queue and execute the command later, when the simulation reaches that point in the scenario.
		Implementation In C++, you can bind a command to a document by passing the document as a parameter in the constructor for the command.
	www.adapower.org /alg/command.html (393 words)

	Command Pattern
		Note that the act of pushing a new command to the command stack truncates the stack at that point, discarding all of the command objects after the current top-of-stack stack entry.
		When pushing to the stack, if a command execution fails, this class also undoes the commands done so far (which rolls state back to the way it was before the group was executed) then it fails the creation of the group object.
		I focus on undo because the command pattern is a very intuitive and extensible way to implement it.
	c2.com /cgi/wiki?CommandPattern (1322 words)

	Command Pattern (Site not responding. Last check: 2007-09-19)
		Command Pattern encapsulates a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
		The key to this pattern is an abstract Command class, which declares an interface for executing operations.
		Concrete Command subclasses specify a receiver-action pair by storing the receiver as an instance variable and by implementing Execute to invoke the request.
	www.instantiations.com /codepro/ws/docs/features/patterns/command_pattern.html (553 words)

	Implementing the Command Pattern in .Net
		The command pattern is a very useful pattern when you want to give your users the ability to do certain things and undo them.
		This functionality is accomplished with the command pattern.
		The interfaces allow different kinds of commands to be acted upon as the same type of class.
	blogs.vbcity.com /jspano/articles/198.aspx (391 words)

	Microsoft België & Luxemburg - MSDN - The Command Pattern In Windows Presentation Foundation:
		This design pattern basically abstracts all actions the user can perform in an application into the notion of "commands"; it has been implemented in many different ways on top of various UI frameworks, but now, it has finally made it into the gut of the system itself.
		According to its original description in the famous "Design Patterns" book by the so-called Gang of Four, the Command pattern allows you to "encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations".
		A command binding basically keeps track of a command, and provides four routed events that allow you to preview or handle the invocation of the event (PreviewExecuted and Executed, respectively), and that provide a means for you to indicate if the command can currently execute (PreviewCanExecute and CanExecute, respectively).
	www.microsoft.com /belux/msdn/nl/community/columns/jdruyts/wpf_commandpattern.mspx (3511 words)

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