An Ember helper to project a promise into a stream of POJO states

wrap-promise-helper.js

import Ember from 'ember';

export default Ember.Helper.extend({
  compute([promise]) {
    if (this.promise !== promise) {
      this.promiseState = new PromiseState();
      this.promise = promise;
      this.promise.then((result)=> {
        this.promiseState = this.promiseState.resolve(result);
        this.recompute();
      }).catch((reason)=> {
        this.promiseState = this.promiseState.reject(reason);
        this.recompute();
      });
    }

    return this.promiseState;
  }
});

class PromiseState {
  constructor(attrs = {isResolved: false, isRejected: false}) {
    Object.assign(this, attrs);
  }

  get isPending() {
    return this.isResolved === false && this.isRejected === false;
  }

  get isSettled() {
    return !this.isPending;
  }
  
  resolve(result) {
    return new PromiseState({
      isResolved: true,
      isRejected: false,
      result: result
    });
  }
  reject(reason) {
    return new PromiseState({
      isResolved: false,
      isRejected: true,
      reason: reason
    });
  }
}