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// Copyright 2006 The Closure Library Authors. All Rights Reserved.
//
// 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.
/**
* @fileoverview Implementation of DataNode for wrapping JSON data.
*
*/
goog.provide('goog.ds.JsonDataSource');
goog.require('goog.Uri');
goog.require('goog.dom');
goog.require('goog.ds.DataManager');
goog.require('goog.ds.JsDataSource');
goog.require('goog.ds.LoadState');
goog.require('goog.ds.logger');
/**
* Data source whose backing is a JSON-like service, in which
* retreiving the resource specified by URL with the additional parameter
* callback. The resource retreived is executable JavaScript that
* makes a call to the named function with a JavaScript object literal
* as the only parameter.
*
* Example URI could be:
* http://www.google.com/data/search?q=monkey&callback=mycb
* which might return the JS:
* mycb({searchresults:
* [{uri: 'http://www.monkey.com', title: 'Site About Monkeys'}]});
*
* TODO(user): Evaluate using goog.net.Jsonp here.
*
* A URI of an empty string will mean that no request is made
* and the data source will be a data source with no child nodes
*
* @param {string|goog.Uri} uri URI for the request.
* @param {string} name Name of the datasource.
* @param {string=} opt_callbackParamName The parameter name that is used to
* specify the callback. Defaults to 'callback'.
*
* @extends {goog.ds.JsDataSource}
* @constructor
*/
goog.ds.JsonDataSource = function(uri, name, opt_callbackParamName) {
goog.ds.JsDataSource.call(this, null, name, null);
if (uri) {
this.uri_ = new goog.Uri(uri);
} else {
this.uri_ = null;
}
/**
* This is the callback parameter name that is added to the uri.
* @type {string}
* @private
*/
this.callbackParamName_ = opt_callbackParamName || 'callback';
};
goog.inherits(goog.ds.JsonDataSource, goog.ds.JsDataSource);
/**
* Default load state is NOT_LOADED
* @private
*/
goog.ds.JsonDataSource.prototype.loadState_ = goog.ds.LoadState.NOT_LOADED;
/**
* Map of all data sources, needed for callbacks
* Doesn't work unless dataSources is exported (not renamed)
*/
goog.ds.JsonDataSource['dataSources'] = {};
/**
* Load or reload the backing data for this node.
* Fires the JsonDataSource
* @override
*/
goog.ds.JsonDataSource.prototype.load = function() {
if (this.uri_) {
// NOTE: "dataSources" is expose above by name so that it will not be
// renamed. It should therefore be accessed via array notation here so
// that it also doesn't get renamed and stops the compiler from complaining
goog.ds.JsonDataSource['dataSources'][this.dataName_] = this;
goog.ds.logger.info('Sending JS request for DataSource ' +
this.getDataName() + ' to ' + this.uri_);
this.loadState_ = goog.ds.LoadState.LOADING;
var uriToCall = new goog.Uri(this.uri_);
uriToCall.setParameterValue(this.callbackParamName_,
'JsonReceive.' + this.dataName_);
goog.global['JsonReceive'][this.dataName_] =
goog.bind(this.receiveData, this);
var scriptEl = goog.dom.createDom('script', {'src': uriToCall});
goog.dom.getElementsByTagNameAndClass('head')[0].appendChild(scriptEl);
} else {
this.root_ = {};
this.loadState_ = goog.ds.LoadState.NOT_LOADED;
}
};
/**
* Gets the state of the backing data for this node
* @return {goog.ds.LoadState} The state.
* @override
*/
goog.ds.JsonDataSource.prototype.getLoadState = function() {
return this.loadState_;
};
/**
* Receives data from a Json request
* @param {Object} obj The JSON data.
*/
goog.ds.JsonDataSource.prototype.receiveData = function(obj) {
this.setRoot(obj);
this.loadState_ = goog.ds.LoadState.LOADED;
goog.ds.DataManager.getInstance().fireDataChange(this.getDataName());
};
/**
* Temp variable to hold callbacks
* until BUILD supports multiple externs.js files
*/
goog.global['JsonReceive'] = {};
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