In my angular 4 application I have to load a thumbnail, So I have img [src] tag. To append the authorization token at the request to load this image I use a custom image pipe and an async pipe. It works good but if I see in the network tab I can see a strange call to null and I think is the async pipe:
Request URL:http://localhost:4200/null
image.pipe
@Pipe({name: 'image'})
export class ImagePipe implements PipeTransform {
constructor(private http: Http) {}
transform(url: string, selfLink?: any, width?: any) {
/* tell that XHR is going to receive an image as response, so it can be then converted to blob,
* and also provide your token in a way that your server expects */
if (selfLink) {
url = selfLink + url + width;
}
const headers = new Headers({'Authorization': 'Bearer ' + localStorage.getItem('token'), 'Content-Type': 'image/jpeg'});
// specify that response should be treated as blob data
return this.http.get(url, new RequestOptions({headers: headers, responseType: ResponseContentType.Blob}))
.map(response => response.blob()) // take the blob
.switchMap(blob => {
// return new observable which emits a base64 string when blob is converted to base64
return Observable.create(observer => {
const reader = new FileReader();
reader.readAsDataURL(blob); // convert blob to base64
reader.onloadend = function() {
observer.next(reader.result); // emit the base64 string result
}
});
});
}
}
And this is the component.html
<div class="card-avatar" (click)="openFilePicker()">
<img class="img pointer" [ngStyle]="{'width.px': 130,'height.px': 130}" *ngIf="links.avatar && imageLink" [src]="(imageLink | image) | async" />
<img src="../../assets/img/default-avatar.png" class="img pointer" *ngIf="links.avatar === undefined">
</div>
It seems that the async pipe make the call 2 times, 1 is corect and 1 is with error, I don't know why, my image link is never null or undefined because if I print the url in the image pipe I see always the correct link.
this is the call:
Also if I write directly a link into the pipe without any call I still have a null <img [src]="('http://.....:8080/api/v1/medias/1/download' | image) | async" />
How can I solve this null call?
