无法为打字稿字典赋值

Unable to assign value to typescript dictionary

本文关键字：字典 赋值      更新时间：2023-09-26

我创建了一个打字稿字典。当我为它赋值时，出现以下错误。

         TypeError: Cannot set property 'v1/items/someItemType/someItemId/EVENT/some
    DataTypeId' of undefined
          at MainClass.subscribe (G:'Projects'src'main'MainClass
    .js:9:3522)
          at Context.<anonymous> (G:'Projects'test'main'Wish.
    spec.js:45:18)
          at callFn (G:'Projects'node_modules'mocha'lib'runna
    ble.js:315:21)
          at Hook.Runnable.run (G:'Projects'node_modules'moch
    a'lib'runnable.js:308:7)
          at next (G:'Projects'node_modules'mocha'lib'runner.
    js:298:10)
          at Immediate._onImmediate (G:'Projects'node_modules
    'mocha'lib'runner.js:320:5)

以下是我声明字典的方式。

interface StringTopicToMyTopicMap {
  [topic: string]: MyTopic;
};

下面是MyTopic的界面。

export interface MyTopic {
  dataTypeID: string;
  itemID: string;
  itemType: string;
  dataType: MyDataType;
  qos: number;
}

然后我尝试为这个字典分配值，如下所示。

private subscriptionTopicsMap: StringTopicToMyTopicMap;
subscribe(myTopic: MyTopic) {
    if (_.isEmpty(myTopic)) {
      throw new MyError('myTopic cannot be empty');
    } else {
      let topic: string;
      topic = 'v1/items/' + myTopic.itemType + '/' + myTopic.itemID + '/'
        + myTopic.dataType + '/' + myTopic.dataTypeID;
      this.subscriptionTopicsMap[topic] = myTopic;
      this.client.subscribe(topic);
    }
  }

错误从行中抛出，

this.subscriptionTopicsMap[topic] = myTopic;

我是打字稿的新手。我在这里做错了什么？请指教。

我通常以更简单的方式执行此操作，不需要第二个界面。同样作为之前的答案，您将需要如下={}：

private subscriptionTopicsMap: { [id: string]: MyTopic; } = {};
this.subscriptionTopicsMap[topic] = myTopic;

只需在声明时初始化您的属性

//private subscriptionTopicsMap: StringTopicToMyTopicMap;
private subscriptionTopicsMap: StringTopicToMyTopicMap = {};

您尚未初始化subscriptionTopicsMap字典，此外，您没有任何实现StringTopicToMyTopicMap的类，并且可以实例化

  class StringTopicToMyTopicMapClass implements StringTopicToMyTopicMap {
         [topic: string]: MyTopic;
  };
  private subscriptionTopicsMap: StringTopicToMyTopicMap = new StringTopicToMyTopicMapClass ();
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