TypeScript实现状态模式的示例代码

interface State {
    handleRequest(context: DocumentContext): void;
}

class DraftState implements State {
    handleRequest(context: DocumentContext): void {
        console.log("Document is in draft state.");
        context.setState(new ReviewState()); // 转换状态为审查状态
    }
}

class ReviewState implements State {
    handleRequest(context: DocumentContext): void {
        console.log("Document is under review.");
        context.setState(new PublishedState()); // 转换状态为发布状态
    }
}

class PublishedState implements State {
    handleRequest(context: DocumentContext): void {
        console.log("Document is published.");
        // 这里可以选择不转换状态
    }
}

class DocumentContext {
    private state: State;

    constructor(initialState: State) {
        this.state = initialState;
    }

    setState(state: State): void {
        this.state = state;
    }

    request(): void {
        this.state.handleRequest(this);
    }
}

// 使用示例
const document = new DocumentContext(new DraftState());

// 处理请求，转换状态
document.request(); // 输出: Document is in draft state.
document.request(); // 输出: Document is under review.
document.request(); // 输出: Document is published.