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POGetting a Filter to handle a Promised Service
 

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  1. POGetting a Filter to handle a Promised Service
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    <p>I have already started to rework this code to operate synchronously, but out of curiosity and a desire to support both means, I need some help understanding how to get a filter to jive with a promise. As some other posts mention a filter seems to just resolve to {} from a promise.</p> <h2>Basic Pattern</h2> <p>Here's a breakdown:</p> <ol> <li><p>Define a service in the module that returns a promise instead of an object</p> <pre><code>module.factory('promisedSvc', ['$http', function($http) { var httpPromise = null, servicePromise = null, service = {}, dataSet = {}; var httpPromise = $http.get('somedata.json').success(function(data) { dataSet = data; }); servicePromise = httpPromise.then(function(){ service.getData = function(key) { return dataSet[key]; }; service.addData = function(key, value) { dataSet[key] = value; }; return service; }); /* In actuality I proxied the service methods onto the promise because I didn't want consumers of the service to have to deal with it being a promise. There is the caveat of setting properties on a class I don't own (property collisions), a risk I'm okay taking, but YMMV Commented out proxies servicePromise.getData = function(key) { return this.then(function(svc){ return svc.getData(key); }); }; servicePromise.addData = function(key, value) { this.then(function(svc){ svc.addData(key, value); }); }; */ return servicePromise; }]); </code></pre></li> <li><p>Controllers can handle this <code>promisedSvc</code> fine, you just get the promise injected into the controller and then use the <code>then</code> function on the promise to wrap the setting of a <code>$scope</code> property to the function call on the eventual service object: <code>getData(key)</code> or <code>setData(key, value)</code>. Alternately you can just treat it as normal if you proxied the functions onto the promise like in the commented out block.</p></li> <li><p>Filters do not seem to inherently handle promises like <code>$scope</code> does. I am looking for a way to get the filter to inject the <code>promisedSvc</code> and be able to call <code>getData(key)</code> without it resolving to <code>{}</code> because the promise has not resolved yet. Below is an example of what does not work:</p> <pre><code>module.filter('svcData', ['promisedSvc', function(promisedSvc) { return function(input) { return promisedSvc.then(function(svc) { var value = svc.getData(input); return value; }); }; }]); </code></pre></li> </ol> <p>So is there a way to write the filter to be able to resolve the value?</p> <h2>Use Case</h2> <p>That is the simplified pattern of what I am trying to achieve. For those curious, my actual use case is to pre-fetch i18n/l10n resource bundle information so I can localize all the text in my application. The pre-fetch could all be in the Javascript environment (attached to some already loaded global or in a provider), but we also have scenarios with database-stored Resource Bundles so I needed a version of code that can pre-fetch all the information from the server via AJAX.</p>
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