反应:渲染箭头函数内定义的方法? [英] React: Rendering a method defined inside arrow function?

问题描述

你好朋友！我希望你一切都好.

Hello friends! I hope you are well.

我有一个名为WorldInfo的箭头函数，它的父组件正在向下传递props中的对象.为了这个示例，我只是调用object.现在在WorldInfo中，我也想解析并列出object中的items，因此我创建了方法serverInfoTabList来使用object并将其推入.map.我的问题是编译时，我的浏览器在定义serverInfoTabList或在WorldInfo自己的返回函数中调用时都无法识别.

I've got an arrow function called WorldInfo and its parent component is passing down an object in props that for the sake of this example, I'm just calling object. Now In WorldInfo I also want to parse and list the items in object, so I've created the method serverInfoTabList to take object and shove it through .map. My problem is when compiled, my browser does not recognize serverInfoTabList either when it's defined nor called in WorldInfo's own return function.

这是错误和代码本身.

Here is the error and the code itself.

 Line 7:5:    'serverInfoTabList' is not defined  no-undef
 Line 34:22:  'serverInfoTabList' is not defined  no-undef

const WorldInfo = (props) =>  {

    serverInfoTabList = (object) => {
        if (object != undefined){
            return object.item.map((item) => {
                const time = Math.trunc(item.time/60)
                return (
                    <li key={item._id}>{item.name}
                        <br/>
                        Minutes Online: {time}
                    </li>
                );
            });
        }
    }

    return (
        props.object!= undefined ? 
        <div className={props.className}>
            <h1>{props.world.map}</h1>
            {/* <img src={props.object.image}/> */}
            <div>
                <ul>  
                    {serverInfoTabList(props.object)}
                </ul>
            </div>
        </div>
        : 
        null
    );
}

感谢您与我的朋友！

推荐答案

您忘记了const声明

const serverInfoTabList = (object) => {
    /* ... */
}

另一个问题是您正在访问例如props.world不存在的属性.同样，您正在通过未定义的属性props.object.item进行映射.我已经更正了您的沙箱

The other problem is that you're accessing properties which doesn't exist props.world for instance. Also you're mapping through an undefined property props.object.item. I've corrected your sandbox

const WorldInfo = props => {
  const serverInfoTabList = object => {
    return Object.keys(object).map(key => {
      const item = object[key];
      const time = Math.trunc(item.time / 60);
      return (
        <li key={item._id}>
          {item.name}
          <br />
          Minutes Online: {time}
        </li>
      );
    });
  };

  return props.object ? (
    <div className={props.className}>
      <h1>{props.world.map}</h1>
      {/* <img src={props.object.image}/> */}
      <div>
        <ul>{serverInfoTabList(props.object)}</ul>
      </div>
    </div>
  ) : null;
};

class Todo extends Component {
  render() {
    const object = { item1: { _id: 1, time: 1 }, Item2: { _id: 2, time: 2 } };
    return (
      <div>
        <WorldInfo object={object} world={{ map: "foo" }} />
      </div>
    );
  }
}

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