从计算属性返回承诺 [英] Returning a Promise from a Computed Property

问题描述

我意识到有几个与此类似的问题，但是这些答案似乎都无法解决我的问题。我的目标是获取语言的列表，并对其进行过滤，以便我的模板可以显示完整列表的一部分。

I realize there have been several questions similar to this, but none of those answers seems to be resolving my issue. My objective is to take a list of language's, and filter them so that my template can display a subset of the full list.

我首先通过验证自己的计算属性是否正常运行：

I started off by verifying that my computed property is working:

MyController.js

// Works as expected
languagesFiltered: function() {
   return this.get('languages');
}.property('languages')

然后我在过滤器函数中添加了这是我遇到麻烦的地方：

Then I added in a filter function, but here's where I ran into trouble:

MyController.js

languagesFiltered: function() {
   // console.log shows that languages is actually a promise
   var languages = this.get('languages');

   // all of this returns a promise, but Handlebars can't handle the promise
   return languages.then( function( languagesArray ) {
      return languagesArray.filter( function( item, index, enumerable) { 
         return item.get('name') !== 'English';
      });
   })
}.property('languages')

我正在尝试使用 Ember.Array.filter 方法（ http://emberjs.com/api/classes /Ember.ArrayProxy.html#method_filter ）。过滤器似乎正常工作，但是现在 languagesFiltered 返回一个诺言，而车把无法处理。

I'm attempting to use the Ember.Array.filter method (http://emberjs.com/api/classes/Ember.ArrayProxy.html#method_filter). The filter seems to be working correctly, but now languagesFiltered returns a promise, and Handlebars can't handle that.

我尝试了最后一种选择：

I tried one last alternative:

MyController.js

languagesFiltered: function() {
     var languages = this.get('languages');

     // "return languages;" works
     // But "return languages.filter" returns an empty array
     return languages.filter( function( item, index, enumerable ) {
         console.log(item);
         return true;
   });
}.property('languages')

和控制台。 log（item）永远不会被调用。所以我的问题是：

And console.log(item) never gets called. So my questions are:

• 实现我所追求的简单过滤器的最佳方法是什么？


• 这是一个只读的计算属性，但是在计算属性中处理异步值的最佳实践是什么？

I' m使用Ember 1.7.0-beta4，Ember Data 1.0.0-beta10和ember-cli 0.44。我将升级到Ember 1.7.0，但是有一个小错误会影响应用程序的另一部分，因此我们要等到1.7.1。谢谢您的输入！

I'm using Ember 1.7.0-beta4, Ember Data 1.0.0-beta10, and ember-cli 0.44. I'd upgrade to Ember 1.7.0, but there's a small bug that affects another part of our app, so we're waiting until 1.7.1. Thanks for your input!

推荐答案

您可以尝试返回 PromiseArray 而不只是承诺。

You can try returning a PromiseArray instead of just the promise.

您应该可以执行类似操作。

You should be able to do something like..

languagesFiltered: function() {
   // all of this returns a promise, but Handlebars can't handle the promise
   var promise = this.get('languages').then( function( languagesArray ) {
      return languagesArray.filter( function( item, index, enumerable) { 
         return item.get('name') !== 'English';
      });
   })

   return DS.PromiseArray.create({
      promise: promise
   });

}.property('languages')

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