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@AmilKey
Created July 2, 2016 10:30
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New Twiddle
import Ember from 'ember';
import DS from 'ember-data';
/**
* Returns true iff the number passed in is even
* @param {Number} x
* @return {Boolean}
*/
function isEven(x) {
return x % 2 == 0;
}
/**
* Returns a Promise which resolves to true if the number passed in is even,
* and resolves to false otherwise
* @param {Number} x
* @return {Promise<Boolean>}
*/
function isEvenAsync(x) {
return new Ember.RSVP.Promise(function(resolve) {
let result = isEven(x);
resolve(result);
});
}
/* A DS.PromiseArray acts like both an Array and a promise.
* Have a look at its documentation:
* - http://emberjs.com/api/data/classes/DS.PromiseArray.html
* Once the underlying promise of the DS.PromiseArray resolves, its
* `content` property is set to the resulting value of that promise,
* (which should be an Array). This Array can then be used, e.g. in a template.
*
* DS.PromiseArray has a built-in method `filter` (inherited from Ember.ArrayProxy).
* This method takes a single parameter, a function `fn`, which takes a single value
* and returns a Boolean.
* Before the underlying promise of the PromiseArray has resolved, applying `filter`
* gives an empty Array.
* Once the underlying promise of the PromiseArray resolves to an array `a`, `filter`
* returns an array containing only those elements of `a` for which `fn` returns
* true.
* The resulting array can be used, e.g. in a template.
*/
/* Your task is to extend the DS.PromiseArray class with a similar function called
* `filterAsync`, which should have the same effect as `filter` with one subtle
* difference:
* The function `asyncFn`, which `filterAsync` takes as a parameter, takes
* a value, but instead of a Boolean, it returns a Promise which resolves to a
* Boolean.
* E.g. the function `isEvenAsync` above is such a function.
* `filterAsync` should still produce an array once the PromiseArray's underlying
* promise resolves.
*/
DS.PromiseArray.reopen({
/**
* @method filterAsync
* @param {Function<any -> Promise<Boolean>>} asyncFilterFn
* @return {Array}
*/
filterAsync(asyncFn) {
return [42];
}
});
/* filteredModel and asyncFilteredModel below should eventually have the same value.
*/
export default Ember.Controller.extend({
_initModel: Ember.on('init', function() {
this.set('model', DS.PromiseArray.create({
promise: new Ember.RSVP.resolve([0,1,2,3,4,5,6,7,8])
}));
}),
filteredModel: Ember.computed('model.[]', function(){
return this.get('model').filter(isEven);
}),
asyncFilteredModel: Ember.computed('model.[]', function(){
return this.get('model').filterAsync(isEvenAsync);
}),
});
{{#each filteredModel as |n|}}
{{n}}
{{/each}}
<br>
{{#each asyncFilteredModel as |n|}}
{{n}}
{{/each}}
{
"version": "0.10.1",
"EmberENV": {
"FEATURES": {}
},
"options": {
"use_pods": false,
"enable-testing": false
},
"dependencies": {
"jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
"ember": "2.6.0",
"ember-data": "2.6.1",
"ember-template-compiler": "2.6.0"
},
"addons": {}
}
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