How to return a deferred promise and create a model with Ember.Deferred?

问题

I'm trying to create a User.current() in my application, which pulls data from my server using $.getJSON('/users/current', function(data) { ... });. I am using the Singleton method that Discourse uses, which does the following:

Dashboard.Singleton = Ember.Mixin.create({
        // See https://github.com/discourse/discourse/blob/master/app/assets/javascripts/discourse/mixins/singleton.js

        current: function() {
                if (!this._current) {
                        this._current = this.createCurrent();
                }
                return this._current;
        },

        createCurrent: function() {
                return this.create({});
        }
});

And in my User singleton model, I've rewritten createCurrent as follows:

Dashboard.User.reopenClass(Dashboard.Singleton, {
        createCurrent: function() {
                return Ember.Deferred.promise(function(p) {
                        return p.resolve($.getJSON('/users/current').then(function(data) {
                                return Dashboard.User.create(data);
                        }));
                });
        }
});

User is a normal Ember object model:

Dashboard.User = Ember.Object.extend({

});

This does request the data from the server, but the function is not setting User.current() correctly - when I inspect it, User.current() has none of the properties that should be set, such as name.

How can I return and set the current user using Ember's deferred and promises?

回答1:

That's cause you're returning the promise in place of the user.

Why don't you create the user, then fill in the properties later.

Or use the Promise Proxy pattern that Ember Data uses (the promise can be used as the object once resolved)

DS.PromiseObject = Ember.ObjectProxy.extend(Ember.PromiseProxyMixin);

function promiseObject(promise) {
  return DS.PromiseObject.create({ promise: promise });
}

回答2:

Since $.getJSON('/users/current') returns a promise, might as well use that.

createCurrent: function() {
                return $.getJSON('/users/current').then(function(data) {
                       return Dashboard.User.create(data);
                });
    }

Then you need to keep in mind that createCurrent returns a promise, not the object itself so you will need to:

current: function() {
            if (!this._current) {
                    var that = this;
                    this.fetching = true;
                    this.createCurrent().then(function(val) {
                        that.fetching = false;
                        that._current = val;
                    });
            }
            return this._current;
    },

来源：https://stackoverflow.com/questions/20597087/how-to-return-a-deferred-promise-and-create-a-model-with-ember-deferred

标签

ember.js