How to access store in second component in react-r

问题:

I have a single component App.js where I trying to save state using redux. In index.js where I set store for only <App /> component.

index.js

let store = createStore(scoreReducer);

ReactDOM.render(
  <Provider store={store}><App /></Provider>,
  document.getElementById("root")
);
registerServiceWorker();

I have this method in App.js to map state to props which is available inside App.js.

App.js

function mapStateToProps(state) {
  return { score: state.score, status: state.status };
}

Everything is well so far, now I am not sure how to access { this.props.score} in another component ?

What changes I need to do in index.js and second component if I want to access {this.props.score} in another component ?

回答1:

When you are using Provider any component that is children of the Provider Higher Order Component can access the store properties though the use of connect function.

So you can add the following in any component that is a child of Provider and access the score prop

function mapStateToProps(state) {
  return { score: state.score, status: state.status };
}

export default connect(mapStateToProps)(MyComponent)

However if this other component is a direct child of App component then you can also pass the score prop as a prop to this component from App like

<MyComponent score={this.props.score}/>

回答2:

Provider component sets the context for all its children, providing the store in it. when you use the High Order Component(HOC) connect you can wrap any component and access the store through the provided mapStateToProps and mapStateToProps no matter how nested they are. You can also access the store using context context.store but this is not recommended. Using map functions and connect, similar to what you have with your App component, is the best approach.