Command Pattern

in Design Patterns
Command Pattern

Command Pattern에 대해 설명하는 페이지입니다.

Environment

  • Programming Language: Java

Index

Introduction

  • Purpose
    • Encapsulates a request as an object
    • This allows the request to be handled in traditionally object based relationships such as queuing and callbacks.
  • Use When
    • Requests need to be specified, queued, and executed at variant times or in variant orders.
    • A history of requests is needed.
    • The invoker should be decoupled from the object handling the invocation.

How to Use (Example)

  • Command Interface
    public interface Command {
    public void execute();
}
  • Implementing a command
    public class MyCommand implements Command {
    MyReceiver myRecevier;

    public MyCommand(MyReceiver myReceiver) {
        this.myReceiver = myReceiver;
    }

    public void execute() {
        // Call a method of myReceiver
        // ex. myReceiver.work();
    }
}
  • Building Invoker
    public class MyInvoker {
    Command slot;

    public MyInvoker() {}

    public void setCommand(Command command) {
        slot = command;
    }

    // Use your own method
    public void buttonPressed() {
        slot.execute();
    }
}
  • Client Program
    public class Main {
    public static void main(String[] args) {
        // Create invoker
        MyInvoker myInvoker = new MyInvoker();

        // Create receiver
        MyReceiver myReceiver = new MyReceiver();

        // Create command
        MyCommand myCommand = new MyCommand(myReceiver);

        // linking the invoker with the command
        myInvoker.setCommand(myCommand);

        myInvoker.buttonPressed();
    }
}





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