React Prop渲染为对象 - 不明白为什么

Question

I'm new to React, and I just can't figure this out...

I'm trying to pass my state to a prop in the parent component, and then render that state in a child component. Like so:

Parent Component

class App extends Component {
   constructor(props) {
      super(props);
      this.state = {
         text: 'hello'
      }
   }
   render() {
      return (
         <div className="App">
            <MessageList textProp={this.state.text}/>
         </div>
      );
   }
}

Child Component

const MessageList = textProp => {
   return (
   <div className='MessageList'>
      {textProp}
   </div>
   )
}

React won't render properly, claiming it is an object that is trying to be rendered.

I can access the property by using {textProp.textProp} , why is it rendering an object which contains a property of the same name?

I'm sure this is very simple but I could do with an explanation!

Thanks in advance.

Answer 1

Components' props are an object, just as their state is an object. Therefore you want something more like:

const MessageList = props => {
   return (
   <div className='MessageList'>
      {props.textProp}
   </div>
   )
}

or, using destructuring:

const MessageList = ({ textProp }) => {
   return (
   <div className='MessageList'>
      {textProp}
   </div>
   )
}

Answer 2

When you declare stateless component you need to specify the arguments you want it to receive it can be (props) or ({ specific }) in your case:

const MessageList = ({ textProp }) => (
 <div className='MessageList'>
      {textProp}
   </div>
);

Note how i do => () that will return the markup, you don't have do to { return () } just a tip to run things better :)

Answer 3

The textProp in MessageList is a collection of props form the parent. In your case the collection will have only textProp. To make this work you need to do the following.

const MessageList = ( {textProp} ) => {
   return (
   <div className='MessageList'>
      {textProp}
   </div>
   )
}

or

const MessageList = (textProp) => {
   return (
   <div className='MessageList'>
      {textProp.textProp}
   </div>
   )
}