It seems in rxjs 4.x, Rx.Observable.fromCallback accept scope as the second parameter, but in 5.0, this method is changed to Rx.Observable.bindCallback and doesn't accept scope parameter. How to add scope parameter in bindCallback. For example in ES6.

class Test {
  constructor(input) {
    this.input = input;
  }

  callback(cb) {
    return cb(this.input);
  }

  rx() {
    // this works on rx 4.x
    // var observable = Rx.Observable.fromCallback(this.callback, this)();

    // this doesn't work, because this.callback function doesn't use original this, so cannot get this.input
    var observable = Rx.Observable.bindCallback(this.callback)();

    // Work around: Rx.Observable.bindCallback(this.callback)();
    // var me = this;
    // var observable = Rx.Observable.bindCallback((cb) => {me.callback(cb);})();

    observable.subscribe(
      input => console.log('get data => ' + input),
      err => console.log('get error =>' + err),
      () => console.log('plete')
    );
   }
  }

  new Test(100).rx();

It seems in rxjs 4.x, Rx.Observable.fromCallback accept scope as the second parameter, but in 5.0, this method is changed to Rx.Observable.bindCallback and doesn't accept scope parameter. How to add scope parameter in bindCallback. For example in ES6.

class Test {
  constructor(input) {
    this.input = input;
  }

  callback(cb) {
    return cb(this.input);
  }

  rx() {
    // this works on rx 4.x
    // var observable = Rx.Observable.fromCallback(this.callback, this)();

    // this doesn't work, because this.callback function doesn't use original this, so cannot get this.input
    var observable = Rx.Observable.bindCallback(this.callback)();

    // Work around: Rx.Observable.bindCallback(this.callback)();
    // var me = this;
    // var observable = Rx.Observable.bindCallback((cb) => {me.callback(cb);})();

    observable.subscribe(
      input => console.log('get data => ' + input),
      err => console.log('get error =>' + err),
      () => console.log('plete')
    );
   }
  }

  new Test(100).rx();

• javascript
• rxjs5

Share Improve this question Follow edited Jun 14, 2017 at 20:05 Bielik 99222 gold badges1515 silver badges2626 bronze badges asked Mar 28, 2016 at 7:36 ramon.liuramon.liu 18633 silver badges55 bronze badges

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2 Answers 2

Sorted by: Reset to default 4

There is an example at http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#static-method-bindCallback which shows how to do this.

Use bindCallback on object method

const boundMethod = Rx.Observable.bindCallback(someObject.methodWithCallback); boundMethod.call(someObject) // make sure methodWithCallback has access to someObject .subscribe(subscriber);

You can call it immediately without declaring a variable, and also pass args like this:

Rx.Observable.bindCallback(someObject.callback).call(someObject,<args>)

So to bind to this you can simply call

Rx.Observable.bindCallback(this.callback).call(this,<args>)

It works for me, when I add this to the constructor

  constructor(input) {
    this.input = input;
    this.callback = this.callback.bind(this)
  }