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POQ - wait for operation to complete before invoking next operation
 

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  1. POQ - wait for operation to complete before invoking next operation
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    <p>Within the primeData call in datacontext there are four queries to a back-end Web API service:</p> <pre><code>function primeData(forceRefresh) { return (getLookups(forceRefresh) // this needs to complete before moving on .then(success)) .then(model.initialize(datacontext)) // depends on getLookups .then(getDatasetOne()) // depends on model.initialize .then(getDataSetTwo()) // depends on model.initialize .then(getNonDependantDataset); // doesn't depend on previous calls function success(data) { if (!initialized) { datacontext.lookups = data.results[0]; initialized = true; } else { datacontext.lookups = { teams: getLocal('Teams', 'id'), // other lookup values here }; } // should I call model.initialize(datacontext) here?? } } </code></pre> <p>Queries 2 and 3 (getDatasetOne() and getDatasetTwo()) are dependent on model.initialize - which is dependent of the results of the first query (getLookups()). I would like to understand how to ensure that model.initialize is not invoked until getLookups has successfully completed - and ensure that getDatasetOne/Two aren't called until the model has been initialized. I've reduced/simplified the code as much as possible to show the complete picture. Clearly, I do not understand Q. Any assistance would be greatly appreciated. </p> <p>CONTROLLER:</p> <pre><code>'use strict'; app.controller('HomeController', ['$scope', 'breeze', 'datacontext', 'logger', function HomeController($scope, breeze, datacontext, logger) { function initialize(forceRefresh) { datacontext.initialize(forceRefresh) .then(getSucceeded) .fail(queryFailed) .fin(refreshView); } initialize(); $scope.refresh = refresh; function refresh() { initialize(true); } function getSucceeded() { $scope.lookups = datacontext.lookups; $scope.datasetOne = datacontext.datasetOne; $scope.datasetTwo = datacontext.datasetTwo; } function refreshView() { $scope.$apply(); } function queryFailed(error) { logger.error(error); } }]); </code></pre> <p>DATACONTEXT:</p> <pre><code>app.factory('datacontext', ['breeze', 'Q', 'logger', 'model', function (breeze, q, logger, model) { var initialized; var manager = configureBreezeManager(); var datacontext = { initialize: initialize, metadataStore: manager.metadataStore, saveEntity: saveEntity }; return datacontext; //#region private members function initialize(forceRefresh) { if (!initialized || forceRefresh) { return primeData(forceRefresh).then(function () { logger.log("Running Initialize"); }); } else { logger.log("Already Initialized"); return q(); } } function primeData(forceRefresh) { return (getLookups(forceRefresh) .then(success)) .then(model.initialize(datacontext)) .then(getDatasetOne()) .then(getDataSetTwo()) .then(getNonDependantDataset); function success(data) { if (!initialized) { datacontext.lookups = data.results[0]; initialized = true; } else { datacontext.lookups = { teams: getLocal('Teams', 'id'), // other lookup values here }; } // should I call model.initialize(datacontext) here?? } } function getLookups(forceRefresh) { var query = breeze.EntityQuery .from('Lookups'); if (initialized &amp;&amp; !forceRefresh) { return true; } return manager.executeQuery(query); } function getDatasetOne() { var query = breeze.EntityQuery .from("EntityNameOne"); return manager.executeQuery(query).then(getSucceeded); function getSucceeded(data) { datacontext.datasetOne = model.process(data.results) return q(); } } function getDatasetTwo() { var query = breeze.EntityQuery .from("EntityNameTwo"); return manager.executeQuery(query).then(getSucceeded); function getSucceeded(data) { datacontext.datasetTwo = model.process(data.results); return q(); } } function getNonDependentDataset() { var query = breeze.EntityQuery .from('EntityNameThree'); return manager.executeQuery(query).then(success); function success(data) { datacontext.nonNependentDataset = data.results; } } function saveEntity(masterEntity, message) { // standard implementation } function getLocal(resource, ordering) { var query = breeze.EntityQuery.from(resource) .orderBy(ordering); return manager.executeQueryLocally(query); } function configureBreezeManager() { // standard implementation } }]); </code></pre> <p>MODEL:</p> <pre><code>app.factory('model', ['logger', function (logger) { var datacontext; extendDatasetOne(); extendDatasetTwo(); var model = { initialize: initialize, getDatasetOne: getDatasetOne, getDatasetTwo: getDatasetTwo }; return model; function initialize(context) { datacontext = context; } function getDatasetOne(input) { var ret = []; for (var i = 0; i &lt; input.length; i++) { var item = new TypeOne(input[i]); ret.push(item); } return ret; } function getDatasetTwo(input) { var ret = []; for (var i = 0; i &lt; input.length; i++) { var item = new TypeTwo(input[i]); ret.push(item); } return ret; } function TypeOne(item) { var self = this; for (var prop in item) { if (item.hasOwnProperty(prop)) { self[prop] = item[prop]; } } self.name = getNameForId(item.id); } function TypeTwo(item) { var self = this; for (var prop in item) { if (item.hasOwnProperty(prop)) { self[prop] = item[prop]; } } self.name = getNameForId(item.id); } function extendDatasetOne() { // add properties to prototype } function extendDatasetOne() { // add properties to prototype } function getNameForId(id) { var set = datacontext.lookups.items; for (var i = 0; i &lt; set.length; i++) { if (id == set[i].id) { return set[i].name; } } return null; } }]); </code></pre>
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