React Redux - Why mapStateToProps is called before constructor?

问题

Two questions:

1. Why mapStateToProps is called before constructor?

2. As a side-effect of 1

   constructor (props) { base(props) // props already have values from "mapStateToTprops" }

why that is being done automagically?

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

Update 1

If I want to write a condition like:

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

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)?

回答1:

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)

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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

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

来源：https://stackoverflow.com/questions/39618767/react-redux-why-mapstatetoprops-is-called-before-constructor