Angular-无法在委托函数中设置undefined的属性

问题描述

我通过一种执行两种功能的通用方法来调用服务，一种执行成功，另一种执行失败。该调用已正确执行，但是在成功函数中，我有一个要分配给服务结果值的变量，但是发生的是，它生成错误“无法设置未定义的属性'resultService'”。在下面，我添加了我正在使用的代码段

CallWS.Service.ts

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</html>

AppComponent.ts

export class CallWSService {
  constructor(private http: HttpClient) { }

  callgetmethodExample(urlService: string,responseFunc: (responseParam: any) => any,doInError?: (outService: any) => any) {
    return this.http.get(urlService).subscribe(
      data => (responseFunc(data)),error => (doInError(error))
    )
  }
}

发生的错误是，当尝试分配resultService变量的值时，它会产生以下错误，我不明白为什么会发生这种情况

Error generate

似乎无法识别该变量，并且会生成错误

解决方法

问题是典型的js问题-上下文丢失。要修复它，请使用箭头功能：

this.invokeService.callGetMethodExample(url,result => this.responseFunc(result));

使用这段代码responseFunc不会失去上下文

angular angular delegates