namespaceRefactoringGuru.DesignPatterns.Command.Conceptual { // The Command interface declares a method for executing a command. publicinterfaceICommand { voidExecute(); }
// Some commands can implement simple operations on their own. classSimpleCommand : ICommand { privatestring _payload = string.Empty;
publicvoidExecute() { Console.WriteLine($"SimpleCommand: See, I can do simple things like printing ({this._payload})"); } }
// However, some commands can delegate more complex operations to other // objects, called "receivers." classComplexCommand : ICommand { private Receiver _receiver;
// Context data, required for launching the receiver's methods. privatestring _a;
privatestring _b;
// Complex commands can accept one or several receiver objects along // with any context data via the constructor. publicComplexCommand(Receiver receiver, string a, string b) { this._receiver = receiver; this._a = a; this._b = b; }
// Commands can delegate to any methods of a receiver. publicvoidExecute() { Console.WriteLine("ComplexCommand: Complex stuff should be done by a receiver object."); this._receiver.DoSomething(this._a); this._receiver.DoSomethingElse(this._b); } }
// The Receiver classes contain some important business logic. They know how // to perform all kinds of operations, associated with carrying out a // request. In fact, any class may serve as a Receiver. classReceiver { publicvoidDoSomething(string a) { Console.WriteLine($"Receiver: Working on ({a}.)"); }
publicvoidDoSomethingElse(string b) { Console.WriteLine($"Receiver: Also working on ({b}.)"); } }
// The Invoker is associated with one or several commands. It sends a // request to the command. classInvoker { private ICommand _onStart;
// The Invoker does not depend on concrete command or receiver classes. // The Invoker passes a request to a receiver indirectly, by executing a // command. publicvoidDoSomethingImportant() { Console.WriteLine("Invoker: Does anybody want something done before I begin?"); if (this._onStart is ICommand) { this._onStart.Execute(); }
Console.WriteLine("Invoker: Does anybody want something done after I finish?"); if (this._onFinish is ICommand) { this._onFinish.Execute(); } } }
classProgram { staticvoidMain(string[] args) { // The client code can parameterize an invoker with any commands. Invoker invoker = new Invoker(); invoker.SetOnStart(new SimpleCommand("Say Hi!")); Receiver receiver = new Receiver(); invoker.SetOnFinish(new ComplexCommand(receiver, "Send email", "Save report"));
invoker.DoSomethingImportant(); } } }
执行结果:
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Invoker: Does anybody want something done before I begin? SimpleCommand: See, I can do simple things like printing (Say Hi!) Invoker: ...doing something really important... Invoker: Does anybody want something done after I finish? ComplexCommand: Complex stuff should be done by a receiver object. Receiver: Working on (Send email.) Receiver: Also working on (Save report.)