javascript - React.js setState of objects 属性从数组

Question

现在我需要递增/递减状态对象数组的属性值。我已经尝试将我想到的所有内容都扔给 setState。有时它没有抛出任何错误，但也没有更新值现在我收到错误消息:

this.state.products[key] is undefined

constructor(props) {

    super(props)

    var products = [
        { name: "Motorhead glasses", price: 300, amount: 1 },
        { name: "Judaspriest glasses", price: 499, amount: 1 }
    ]

    this.state = { products: products }
    this.handleMinus = this.handleMinus.bind(this)

}


handleMinus(key) {
    var stateCopy = Object.assign({}, this.state);
    stateCopy.products = stateCopy.products.slice();
    stateCopy.products[key] = Object.assign({}, stateCopy.products[key]);
    stateCopy.products[key].amount += 1;
    this.setState({ [this.state.products[key].amount]: stateCopy });
    console.log(this)
}

Answer 1

你你克隆了一个状态对象，你可以直接修改它并回退到状态

handleMinus(key) {
    var stateCopy = [...this.state.products];   /Create a copy of products array using spread operator syntax.
    stateCopy[key].amount += 1;
    this.setState({products : stateCopy });

}

如果您想知道[...this.state.products] 是什么意思，请查看此答案:What is the meaning of this syntax "{...x}" in Reactjs