value: function (typeOrQuery) {
var type = typeOrQuery instanceof ObjectDescriptor && typeOrQuery,
query = type && DataQuery.withTypeAndCriteria(type) || typeOrQuery,
stream = new this();
stream.query = query;
return stream;
}
value: function (type, object, propertyName, prerequisitePropertyNames, criteria) {
var self, selector, prerequisites, stream;
// Create and cache a new fetch promise if necessary.
if (!this._getCachedFetchPromise(object, propertyName)) {
// Parse arguments.
if (arguments.length >= 4) {
selector = DataQuery.withTypeAndCriteria(type, arguments[arguments.length - 1]);//RDW unclear if there's any special change required here for formal Criteria
} else {
selector = DataQuery.withTypeAndCriteria(type);
}
if (arguments.length < 5 || !prerequisitePropertyNames) {
prerequisites = [];
} else if (!Array.isArray(prerequisitePropertyNames)) {
prerequisites = Array.prototype.slice.call(arguments, 3, -1);
} else {
prerequisites = prerequisitePropertyNames;
}
// Create and cache a new fetch promise
self = this;
this._setCachedFetchPromise(object, propertyName, this.nullPromise.then(function () {
// First get prerequisite data if necessary...
return self.rootService.getObjectProperties(object, prerequisites);
}).then(function () {
// Then fetch the requested data...
stream = self.rootService.fetchData(selector);
return stream;
}).then(function () {
// Then wait until the next event loop to ensure only one
// fetch is dispatched per event loop (caching ensures all
// subsequent requests for the same fetch promise within the
// same event loop will return the same promise)...
return self.eventLoopPromise;
}).then(function () {
// Then removes the promise from the cache so subsequent
// requests for this fetch promise generate new fetches.
self._setCachedFetchPromise(object, propertyName, null);
return stream.data;
}));
}
// Return the created or cached fetch promise.
return this._getCachedFetchPromise(object, propertyName);
}