从组件角度监听服务变量变化 [英] listen to service variable change from component angular

问题描述

我有变量服务和将数​​据带入该变量的方法

I have service with variable and method that brings data to that variable

export class UserService {
  userDetails;
  getUserProfile(){
    return this.http.get(this.BaseURI+'/UserProfile').subscribe(
      res=>{
        this.userDetails=res;
      //  console.log(res);
      },
      err=>{
        console.log(err);
      }
    );
  }

现在我想在变量更改时从组件中检查并读取它.我该怎么做?

now I want to check from component when the variable changes and read it. How can I do that ?

更新.

export class UserService {
  userDetails;

  getUserProfile(){
  this.http.get(this.BaseURI+'/UserProfile').subscribe(
    res=>{
      this.userDetails=res;
    },
    err=>{
      console.log(err);
    }
  )
  }

在组件中我有这个:

  ngOnInit() {
    this.service.userDetails.subscribe((userDetails) =>this.userDetails=userDetails)
  }

现在当我运行应用程序时，组件中出现错误:

Now When I run the app I get error in component:

AppComponent.html:2 错误类型错误:无法读取属性订阅"未定义的

AppComponent.html:2 ERROR TypeError: Cannot read property 'subscribe' of undefined

推荐答案

相信你的get请求完成后基本上需要组件中的数据了.

I believe you basically need the data in the component when your get request is completed.

解决方案 1:考虑将 userDetails 设为 Observable，.这样你就可以在其中的值发生变化时收听它

Solution 1: Consider making userDetails as an Observable, . This way you could listen to it when the value in it changes

export class UserService {

    private _userDetails: Subject<any> = new Subject<any>();    // consider putting the actual type of the data you will receive
    public userDetailsObs = this._userDetails.asObservable();
    getUserProfile(){
        return this.http.get(this.BaseURI+'/UserProfile').subscribe(
          res=>{
            this._userDetails.next(res)
          //  console.log(res);
          },
          err=>{
            console.log(err);
          }
        );
    }
}

在您的组件内部

constructor(private _userService: UserService) {}

ngOnInit() {
    this._userService.userDetailsObs.subscribe((userDetails) => {
        console.log(userDetails)
    })
}

<小时>

解决方案 2. 考虑只返回 HTTP observable 本身.

---

Solution 2. Consider just returning the HTTP observable itself.

getUserProfile(){
    return this.http.get(this.BaseURI+'/UserProfile');
}

在您的组件内部

constructor(private _userService: UserService) {}

ngOnInit() {
    this._userService.getUserProfile.subscribe((userDetails) => {
        console.log(userDetails)
    })
}

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