Angular2: switchMap not canceling previous http calls

Question

I am trying to use switchMap to cancel any previous http calls in Angular2. The code is basically

var run = ():Observable => {
        var url = \'         


        

Answer 1

The requests need to originate from the same underlying stream. Here's a factory function that will create an http service instance that should do what you want:

function httpService(url) {
   // httpRequest$ stream that allows us to push new requests
   const httpRequest$ = new Rx.Subject();

   // httpResponse$ stream that allows clients of the httpService
   // to handle our responses (fetch here can be replaced with whatever
   // http library you're using).
   const httpResponse$ = httpRequest$
       .switchMap(() => fetch(url));


   // Expose a single method get() that pushes a new
   // request onto the httpRequest stream. Expose the
   // httpResponse$ stream to handle responses.
   return {
       get: () => httpRequest$.next(),
       httpResponse$
   };
}

And now the client code can use this service like this:

const http = httpService('http://my.api.com/resource');

// Subscribe to any responses
http.httpResponse$.subscribe(resp => console.log(resp));

// Call http.get() a bunch of times: should only get one log!!
http.get();
http.get();
http.get();