React Native - 将父母的状态传递给孩子的麻烦 [英] React Native - Trouble passing parent's state to child

问题描述

React 新手在从父组件(本例中为 App)传递状态和函数以及从子组件(本例中为 Main)访问时遇到一些问题.我确定这是一两个非常简单的错误，我在哪里被绊倒了?

a React newbie having some issues passing down states and functions from Parent Component (App in this case) and accessing from Child Components (Main in this case). I'm sure it's one or two really simple mistakes, where am I getting tripped up?

这是项目结构:

App
 |__ Rootstack
       |
       |__Favorites
       |__Main

这是精简后的代码:

class Main extends React.Component {
  render() {
      return (
      <View>
         <Text>{this.props.favoritesList.length}</Text>
         <Card>
              onSwiped={() => {this.props.updateArray}} //the idea being that on a swipe, updateArray would add 1 to the 'favoriteList' in the parents state, and the favoritesList.length would update by +1.
         </Card>
      </View>
        );
    }
}

class Favorites extends React.Component {
          ....
    }

const RootStack = StackNavigator(
  {
    Main: {
      screen: Main},
    Favorites: {
      screen: Favorites}
  },
  {
    initialRouteName: 'Main'
  }
);


export default class App extends Component<{}> {
  constructor(props) {
      super(props);
      this.state = {
        favoritesList: []
      };
    this.updateArr = this.updateArr.bind(this); //don't know if this is necessary?
    }

  updateArr=()=>{this.setState({ favoritesList: 
      [...this.state.favoritesList, 'new value']})};

  render() {
      return <RootStack {...this.state} updateArray={this.updateArr}/>;
    }
  }

我得到的错误是 -- 有什么想法吗?提前致谢！

Error I'm getting is -- any ideas? Thanks in advance!

推荐答案

1-

这是不对的

       <Card  ... props should be here!!---  >
          onSwiped={() => {this.props.updateArray}} //the idea being that on a swipe, updateArray would add 1 to the 'favoriteList' in the parents state, and the favoritesList.length would update by +1.
     </Card>

正确答案是:

     <Card  
       onSwiped={() => {this.props.updateArray}} //the idea being that on a swipe, updateArray would add 1 to the 'favoriteList' in the parents state, and the favoritesList.length would update by +1.
      >
    </Card>

错误的意思是Card的孩子应该是一个对象而不是.....

The meaning of the error is that the child of Card is expected to be an object and not .....

2-

this.updateArr = this.updateArr.bind(this); 不是必需的，因为 updateArr = () =>;... 是用 es6 编写的

this.updateArr = this.updateArr.bind(this); is not necessary since updateArr = () => ... is written in es6

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