Question

我正在使用React.js和TypeScript。有没有办法创建从其他组件继承但有一些额外的道具/状态的React组件？

我想要实现的是这样的：

interface BaseStates {
    a: number;
}

class GenericBase<S extends BaseStates> extends React.Component<void, S> {
    protected getBaseInitialState(): BaseStates {
        return { a: 3 };
    }
}

class Base extends GenericBase<BaseStates> {
    getInitialState(): BaseStates {
        return super.getBaseInitialState();
    }
}

interface DerivedStates extends BaseStates {
    b: number;
}

class Derived extends GenericBase<DerivedStates> {
    getInitialState(): DerivedStates {
        var initialStates = super.getBaseInitialState() as DerivedStates; // unsafe??
        initialStates.b = 4;
        return initialStates
    }
}

但是，如果我在this.setState中调用Derived，则会失败，我收到TypeScript错误（DerivedStates类型的参数不能分配给S类型）。我想这不是特定于TypeScript的东西，而是将继承与泛型混合的一般限制（？）。这有什么类型安全的解决方法吗？

更新

我选择的解决方案（根据David Sherret的回答）：

interface BaseStates {
    a: number;
}

class GenericBase<S extends BaseStates> extends React.Component<void, S> {
    constructor() {
        super();
        this.state = this.getInitialState();
    }

    getInitialState(): S {
        return { a: 3 } as S;
    }

    update() {
        this.setState({ a: 7 } as S);
    }
}

interface DerivedStates extends BaseStates {
    b: number;
}

class Derived extends GenericBase<DerivedStates> {
    getInitialState(): DerivedStates {
        var initialStates = super.getInitialState();
        initialStates.b = 4;
        return initialStates;
    }

    update() {
        this.setState({ a: 7, b: 4 });
    }
}

Answer 1

您可以使用类型断言在Derived中一次性设置状态的一些属性：

this.setState({ b: 4 } as DerivedStates); // do this
this.setState({ a: 7 } as DerivedStates); // or this
this.setState({ a: 7, b: 4 });            // or this

顺便说一下，getInitialState不需要有不同的名字......你可以这样做：

class GenericBase<S extends BaseStates> extends React.Component<void, S> {
    constructor() {
        super();        
        this.state = this.getInitialState();
    }

    protected getInitialState() {
        return { a: 3 } as BaseStates as S;
    }
}

class Derived extends GenericBase<DerivedStates> {
    getInitialState() {
        var initialStates = super.getInitialState();
        initialStates.b = 4;
        return initialStates;
    }
}

Answer 2

import { Component } from 'react'


abstract class TestComponent<P = {}, S = {}, SS = any> extends Component<P, S, SS> {
  abstract test(): string
}


type Props = {
  first: string,
  last: string,
}

type State = {
  fullName: string,
}

class MyTest extends TestComponent<Props, State> {
  constructor(props: Props) {
    super(props)
    this.state = {
      fullName: `${props.first} ${props.last}`
    }
  }

  test() {
    const { fullName } = this.state
    return fullName
  }
}

在TypeScript中扩展React组件

2 个答案: