15.命令模式

约 261 字小于 1 分钟

2026-02-27

命令模式（Command Pattern）的主要目的是把“请求”封装成独立命令对象，以支持排队、记录、撤销和重做

适合使用命令模式的场景

调用方只想触发命令，不关心底层执行细节
需要支持撤销/重做等历史回退能力
需要把操作入队延迟执行或批量执行
希望统一记录用户操作日志用于审计或回放

接收者与命令接口

class Editor {
    private text = "";

    append(content: string): void {
        this.text += content;
    }

    removeLast(length: number): void {
        this.text = this.text.slice(0, -length);
    }

    getText(): string {
        return this.text;
    }
}

interface Command {
    execute(): void;
    undo(): void;
}

具体命令与调度者

class AppendTextCommand implements Command {
    constructor(
        private editor: Editor,
        private content: string,
    ) {}

    execute(): void {
        this.editor.append(this.content);
    }

    undo(): void {
        this.editor.removeLast(this.content.length);
    }
}

class CommandManager {
    private history: Command[] = [];

    run(command: Command): void {
        command.execute();
        this.history.push(command);
    }

    undo(): void {
        const command = this.history.pop();
        command?.undo();
    }
}

使用示例

const editor = new Editor();
const manager = new CommandManager();

manager.run(new AppendTextCommand(editor, "Hello "));
manager.run(new AppendTextCommand(editor, "World"));
console.log(editor.getText()); // Hello World

manager.undo();
console.log(editor.getText()); // Hello