reactjs - 浅层 prop 比较对于连接的组件如何工作？

Question

根据 redux 的文档，reducer 总是给出一个新的状态副本。在连接的组件中，react-redux 对 mapStateToProps(旧与新 props)中提到的属性进行浅层比较。

我的困惑是，由于 redux 总是提供新的状态副本，react-redux 进行的浅层比较应该总是给出 false，并且组件应该总是重新渲染。但这并没有发生。

有人可以解释一下我缺少什么吗？

我认为在mapStateToProp中读取的所有属性都是对象。

Answer 1

我们都同意，如果存储状态相同，mapStateToProps 将不会运行。 redux 文档如下:

The wrapper component generated by connect subscribes to the Redux store. Every time an action is dispatched, it calls store.getState() and checks to see if lastState === currentState. If the two state values are identical by reference, then it will not re-run your mapStateToProps function, because it assumes that the rest of the store state hasn't changed either.

答案为 Why isn't my component re-rendering, or my mapStateToProps running?可以描述您的情况，因为您可能不小心直接改变了您的状态。

由于您使用的是“combineReducers”(虽然这很棒)，但还有一个“问题”:

combineReducers utility function tries to optimize state updates. If none of the slice reducers returned a new value, then combineReducers returns the old state object instead of a new one. This means that mutation in a reducer can lead to the root state object not being updated, and thus the UI won't re-render.