使用map时，Reaction‘无法读取未定义的属性’

Question

我正在做一个很基本的应用程序，我经常会遇到“TypeError：无法读取未定义的属性‘onPlayerScoreChange’”即使我正确地绑定了我的函数(我认为)'onPlayerScoreChange'是Grandparent组件，当用户单击“+”或“-”按钮以更改玩家的得分时执行。如果有人能解释一下是怎么回事会很有帮助，因为我想我是在this.onPlayerScoreChange = this.onPlayerScoreChange.bind(this)在曾祖父的构造函数中。父组件：class App extends React.Component {constructor(props) {     super(props);     this.onPlayerScoreChange = this.onPlayerScoreChange.bind(this)     this.state = {         initialPlayers: props.initialPlayers,     };}onPlayerScoreChange(delta, index) {     this.setState((prevState, props) => {         return {initialPlayers: this.prevState.initialPlayers[index].score += delta}     })}render() {     return(         <div className = "scoreboard">             <Header title = {this.props.title}/>             <div className = "players">                 {this.state.initialPlayers.map(function(player, index) {                     return(                         <Player                          name = {player.name}                          score = {player.score}                          key = {player.id}                          index = {index}                         onScoreChange = {this.onPlayerScoreChange}                         />                     )                 })}             </div>         </div>     )}}(组件具有默认标题支持)儿童部分：class Player extends React.Component {render() {     return(         <div className = "player">             <div className = "player-name">                 {this.props.name}             </div>             <div className = "player-score">                 <Counter score = {this.props.score} onChange = {this.props.onScoreChange} index = {this.props.index}/>             </div>         </div>)}}