Each Child in a list should have a unique "key" prop

I'm getting the error "each child in a list should have a unique 'key' prop" error, but I'm confused because I'm attempting to set the key to a unique ID, and it seems like it's not working. I'm using the imdbID as the key, which should be a primary key value (unique and stable). Is my syntax wrong, or what am I doing that's incorrect here ?

import React from 'react';
import "./movie.css";

class Movie extends React.Component {
   render() {
       const {Title, Poster, Year, imdbID} = this.props;

       return (
           <div className="movie" key={imdbID} id={imdbID}>
               <div className="title-year">
                   <h1 className="title">{Title}</h1>
                   <h2 className="year">{Year}</h2>
               </div>
               <div className="poster">
                   <img src={Poster} alt="my movie poster"/>
               </div>
           </div>
       )
   }
}

export default Movie;

And here is the code that's inserting <Movie...> into the application (app.js):

 render() {
   return (
     <div className="App">
       <header className="App-header">
         <Search handleSendRequest={this.sendRequest}/>
         <div className="response">
          {
          this.state.movies && this.state.movies.length ? this.state.movies.map((movie) => {
            return <Movie {...movie}/>
          })
          : null
          }
          
        </div>
       </header>
     </div>
   );
 }

CodePudding user response：

Add a key attribute to your Movie tags and set a unique value. As below

{
  this.state.movies && this.state.movies.length ? this.state.movies.map((movie, index) => {
      return <Movie key={movie.imdbID} { ...movie
      }
      />
    }) :
    null
}

CodePudding user response：

You need the key on <Movie/> itself:

      {
      this.state.movies && this.state.movies.length ? this.state.movies.map((movie) => {
        return <Movie key="HERE" {...movie}/>
      })
      : null
      }

In particular, you need a key every time you iterate over an object. In this case you are iterating over this.state.movies.

You do not need the key inside Movie's render function, where you placed it, because you are not iterating over any object at that time.

CodePudding user response：

The 'key' prop should be inserted at the <Movie/> component, not in the div inside it.