在 componentDidMount() 上设置状态

问题描述

我知道在 componentDidMount 上设置状态是一种反模式，应该在 componentWillMount 上设置状态，但假设我想设置数字的长度li 标签作为一个状态.在这种情况下，我无法在 componentWillMount 上设置状态，因为在该阶段可能尚未安装 li 标记.那么，这里最好的选择应该是什么?如果我在 componentDidMount 上设置状态可以吗?

I know that it is an anti-pattern to set state on componentDidMount and a state should be set on componentWillMount but suppose I want to set the length of the number of li tags as a state. In that case, I can't set the state on componentWillMount since the li tags might not have been mounted during that phase. So, what should be the best option here? Will it be fine if I set the state on componentDidMount?

推荐答案

在 componentDidMount 中调用 setState 不是反模式.事实上，ReactJS 在他们的文档中提供了一个例子:

It is not an anti-pattern to call setState in componentDidMount. In fact, ReactJS provides an example of this in their documentation:

您应该在 componentDidMount 生命周期方法中使用 AJAX 调用填充数据.这样您就可以在检索数据时使用 setState 来更新您的组件.

文档示例

componentDidMount() {
    fetch("https://api.example.com/items")
      .then(res => res.json())
      .then(
        (result) => {
          this.setState({
            isLoaded: true,
            items: result.items
          });
        },
        // Note: it's important to handle errors here
        // instead of a catch() block so that we don't swallow
        // exceptions from actual bugs in components.
        (error) => {
          this.setState({
            isLoaded: true,
            error
          });
        }
      )
  }

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