Question

当我尝试从html调用getHistoryData（）时，出现错误“ ERROR TypeError：无法设置未定义的属性'id'”。

export class Data { 
    id : string ;
    fromTime : any ;
    toTime : any ;
    deviceType : string ;
    interval : any;
    params : string;
}




// payload : Data = {
  //   id : "00:12:4b:00:19:7b:27:7",
  //   fromTime: "1554422400000",
  //   toTime: "1554508799000" ,
  //   deviceType: "xxx",
  //   interval: "1199999",
  //   params: "temperature"
  // }

  payload : Data;

  response : any;


  generatePayload(){
    this.payload.id = "00:12:4b:00:19:7b:27:7",
    this.payload.fromTime = "1554422400000",
    this.payload.toTime = "1554508799000",
    this.payload.deviceType = 'xxx' , 
    this.payload.interval = 1000 ,
    this.payload.params = this.selectedParameter
  }

  getHistoryData(){
    this.generatePayload()
     this.historyDataService.getHistoryData(this.payload)
           .subscribe((data) => this.response = data)
  }

当我如注释代码所示直接分配有效负载对象的值时起作用，但是当我尝试通过函数分配数据时会抛出错误。

Answer 1

因为当您执行payload: Data =时，您正在分配完整的对象。在函数中，您已经期望payload属性与对象值一起存在，但是由于您仅命名了该属性，因此该属性是不确定的。确保为您的属性定义一个初始值，例如payload : Data = {};，然后分配将按预期工作。

Answer 2

仅在定义类型时，需要将this.payload实例化为对象（即打字稿，形状正确的对象）。只需尝试使用新语法将this.payload实例化为Data。

 public payload: Data;

  generatePayload()
  {
    this.payload = new Data(); // will define an object with correct keys.

    this.payload.id = "00:12:4b:00:19:7b:27:7",
    this.payload.fromTime = "1554422400000",
    this.payload.toTime = "1554508799000",
    this.payload.deviceType = 'xxx' , 
    this.payload.interval = 1000 ,
    this.payload.params = this.selectedParameter
  }

Answer 3

您需要先用对象初始化payload属性，然后再为其分配任何值。

payload : Data = {
  id : undefined,
  fromTime: undefined,
  toTime: undefined ,
  deviceType: undefined,
  interval: undefined,
  params: undefined
};

generatePayload(){
  this.payload.id = "00:12:4b:00:19:7b:27:7",
  this.payload.fromTime = "1554422400000",
  this.payload.toTime = "1554508799000",
  this.payload.deviceType = 'xxx' , 
  this.payload.interval = 1000 ,
  this.payload.params = this.selectedParameter
}

如何修复“错误TypeError：无法设置未定义的属性'id'”

3 个答案: