Angular 2 & RxJs catch function callback binding to 'this' causes http request to be repeated over and over

问题

I have a method for handle our errors from http requests and it looks like this

public handleError(err: any, caught: Observable<any>): Observable<any> {

  //irrelevant code removed
  this.logger.debug(err);//example of problem 
  return caught;
}

It is invoked like this (example method, but shows the error)

  public makeHttpCall() {
    this.http.get("http://api.exmaple.com/getsomedata")
      .map(r=> r.json())
      .catch(this.handleError);
  }

The problem with the above code is that when calling this.logger.debug(err) in the handleError method this no longer refers to the class the http call was made from but references the CatchSubscriber.

See here:

So i change .catch(this.handleError); to .catch(this.handlError.bind(this));

This works, now when i call this.logger.debug this refers to the correct object. The problem is, the http request gets called over and over and over, see here:

This only happens after applying .bind(this)

I can't figure out why this is happening

*********EDIT*********

Change from .catch(handleError) to .catch((a,b)=>handleError(a,b)) fixes the reference of this but the http request just gets spammed over and over, but only when the request fails. If the request succeeds it only happens once.

回答1:

When you pass a function with .catch(this.handleError); it loses its context this. See Why do I lose the context of this in Javascript?

Most easily you can fix this by wrapping the function call into a closure.

.catch((err, caught) => this.handleError(err, caught));

来源：https://stackoverflow.com/questions/40149894/angular-2-rxjs-catch-function-callback-binding-to-this-causes-http-request-t