React Redux - 为什么在构造函数之前调用 mapStateToProps? [英] React Redux - Why mapStateToProps is called before constructor?

问题描述

两个问题:

1. 为什么在构造函数之前调用 mapStateToProps?

2. 作为 1 的副作用

1. Why mapStateToProps is called before constructor?

2. As a side-effect of 1

构造函数(道具){基地(道具)//props 已经有来自 "mapStateToTprops" 的值}

为什么会自动完成?

1. 并非每个 mapStateToProps 都会调用 ComponentWillReceiveProps(这是第一次加载时的情况)请参阅此链接 在此处输入链接描述

1. Not every mapStateToProps invokes ComponentWillReceiveProps (this is the case when it loads first time) See this link enter link description here

更新 1

如果我想写一个条件:

Update 1

If I want to write a condition like:

if (props.isAuthenticated) {browserHistory.push("/admin/dashboard")}

哪种方法最适合挂钩.请记住，我想在每次状态更改时强制执行此条件(因为根据 leo 的 答案 ComponentWillReceiveProps 不可靠)?

Which method will be most suitable to hook. Keep in mind that I want to enforce this condition on each state change (because according to leo's answer ComponentWillReceiveProps is not reliable)?

推荐答案

mapStateToProps 不会在构造函数之前神奇地调用.它由 connect 完成，它是一个 <执行 的 href="https://medium.com/@franleplant/react-higher-order-components-in-depth-cf9032ee6c3e#.nho2ygep2" rel="noreferrer">高阶组件mapStateToProps 在你的组件初始化之前.事实上，connect 在它的主体中初始化你的组件.

mapStateToProps is not called magically before your constructor. It is done by connect which is a Higher Order Component that executes mapStateToProps before your component is initialised. In fact, connect initialises your component in its body.

connect(mapStateToProps, mapDispatchToProps)(YourComponent)

<小时>

为什么 componentWillReceiveProps 没有执行?因为 React 不会为初始渲染调用 componentWillReceiveProps，所以你应该使用 componentDidMount 代替.

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Why componentWillReceiveProps not executed? Because React doesn't call componentWillReceiveProps for the initial render, so you should use componentDidMount instead.

componentWillReceiveProps

在组件接收新道具时调用.初始渲染不会调用此方法.

Invoked when a component is receiving new props. This method is not called for the initial render.

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