observeStore.js

// Usage example:
//
// willTransitionTo(transition, params) {
//   transition.wait(
//     observeStore(
//       DraftStore,
//       s => s.isLoaded()
//     ).then(() => {
//       if (DraftStore.isMissingTitle()) {
//         transition.redirect('composeDraft', params);
//       }
//     })
//   );
// }


'use strict';

var Promise = require('bluebird');

function observeStore(store, predicate) {
  var performCheck;

  return new Promise(resolve => {
    performCheck = () => {
      if (predicate.call(null, store)) {
        resolve();
      }
    };

    store.addChangeListener(performCheck);
    performCheck();

  }).finally(() => {
    store.removeChangeListener(performCheck);
  });
}

module.exports = observeStore;