Question

我创建了一个打字稿字典。当我为它赋值时，我收到以下错误。

         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)

以下是我宣布字典的方式。

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

以下是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赋值，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);
    }
  }

从行中抛出错误

this.subscriptionTopicsMap[topic] = myTopic;

我是打字稿的新手。我在这做错了什么？请指教。

Answer 1

宣布

时初始化你的财产

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

Answer 2

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

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

Answer 3

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

  class StringTopicToMyTopicMapClass implements StringTopicToMyTopicMap {
         [topic: string]: MyTopic;
  };

  private subscriptionTopicsMap: StringTopicToMyTopicMap = new StringTopicToMyTopicMapClass ();

希望这会有所帮助!!

无法为typescript字典赋值

3 个答案: