raptor/lib/raptor/data-providers/DataProviders.js

RaptorJS provides an AMD module loader that works in Node, Rhino and the web browser. It also includes various sub-modules to support building optimized web applications.

/*
 * Copyright 2011 eBay Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * The {@link raptor/render-context/Context} class represents a "rendering context"
 * suitable for rendering HTML to a writer. A context object is required when rendering 
 * a template and the context object contains a reference to an underlying writer object that is
 * used to capture the rendered output.
 */
define.Class(
    'raptor/data-providers/DataProviders',
    ['raptor'],
    function(raptor, require) {
        "use strict";
        
        var forEachEntry = raptor.forEachEntry,
            promises = require('raptor/promises');
        
        var DataProviders = function(parent) {
            this.parent = parent;
            this.providers = {};
        };
        
        DataProviders.prototype = {
            register: function(name, func, thisObj) {
                if (typeof name === 'object') {
                    var providers = arguments[0];
                    thisObj = arguments[1];

                    forEachEntry(providers, function(name, func) {
                        this.register(name, func, thisObj);
                    }, this);

                    return;
                }

                this.providers[name] = [func, thisObj];
            },

            hasProvider: function(name) {
                return this.providers.hasOwnProperty(name) || 
                    (this.parent && this.parent.hasProvider(name));
            },

            getProvider: function(name) {
                var provider = this.providers[name];
                if (!provider && this.parent) {
                    return this.parent.getProvider(name);
                }
                else {
                    return provider;
                }
            },

            requestData: function(name, args) {
                var provider = typeof name === 'string' ? this.getProvider(name) : name;
                
                if (!provider) {
                    throw raptor.createError(new Error('Data provider not found for "' + name + '"'));
                }

                var func = provider[0],
                    thisObj = provider[1];

                if (promises.isPromise(func)) {
                    return func;
                }
                
                var deferred;

                try
                {
                    var promise = func.call(thisObj, args);
                    if (!promises.isPromise(promise)) {
                        var value = promise;
                        deferred = promises.defer();
                        deferred.resolve(value);
                        deferred.promise.resolvedValue = value;
                        return deferred.promise;
                    }

                    return promise;
                }
                catch(e) {
                    deferred = promises.defer();
                    deferred.reject(e);
                    return deferred.promise;
                }
            }
        };
        
        
        return DataProviders;
        
    });