Load image from api url into angular 5 component

问题:

I have a component which html structure look like:

<img mat-card-sm-image src="{{img}}" />

and in typescript

constructor(private loginService: LoginService) {
    this.img = null;
    this.loadImage();
  }

loadImage = function () {
   this.img = this.loginService.loginImg();
}

and login service:

loginImg() {
    const url = "http://localhost:59078/api/image/login";
    this.http.get(url, { responseType: 'blob' }).subscribe(result => {
      console.log(result);
      return result;
    });
}

and the API Core controller

  [HttpGet]
  [AllowAnonymous]
  [Produces("image/png")]
  public IActionResult Login()
  {
     var file = Path.Combine(Directory.GetCurrentDirectory(),
                        "wwwroot", "images", "login.png");

     return PhysicalFile(file, "image/png");
  }

The idea that the image is not loaded... Why ?

回答1:

this.http.get(url, { responseType: 'blob' }).subscribe(result => {
  console.log(result);
  return result;
});

the return here does nothing (especially since you aren't returning the http.get iteself). The Service should return the observable http.get (without the subscribe) and then when you subscribe to it from your component, you change the img variable from inside.

Here's how you can fix it

public img: string;

constructor(private loginService: LoginService) {
  this.loadImage();
}

loadImage() {
  this.loginService.loginImg().subscribe(result => {
    this.img = result;
  });
}


# Login service:

loginImg() {
  const url = "http://localhost:59078/api/image/login";
  return this.http.get(url, { responseType: 'blob' });
}

this is unrelated, but you might consider using an Anugular lifecycle hook like ngOnInit instead of the constructor for initializing variables

constructor(private loginService: LoginService) { }

public ngOnInit(): void {
  this.loadImage();
}