How to make Observable from callback

Question

I need to make observable from

window.web3.eth.getCoinbase((error, result) => { ... });

Is it a good idea?

new Observable<string>(o => {
    this.w.eth.getCoinbase((err, result) => {
        o.next(result);
        o.complete();
    });
});

Answer 1

RxJS includes a bindNodeCallback observable creator specifically for creating observables from async functions that use Node-style callbacks.

You could use it like this:

const getCoinbaseAsObservable = Observable.bindNodeCallback(
  callback => this.w.eth.getCoinbase(callback)
);

let coinbaseObservable = getCoinbaseAsObservable();
coinbaseObservable.subscribe(
  result => { /* do something with the result */ },
  error => { /* do something with the error */ }
);

Note that an arrow function is used to ensure the getCoinbase method is called using this.w.ethas its context.