Summary

/**
 * @class
 * This is an implementation of a DataModel used by the Grid. It works 
 * with JSON data.
 * <br>Example schema:
 * <pre><code>
 * var schema = {
 *     root: 'Results.Result',
 *     id: 'ASIN',
 *     fields: ['Author', 'Title', 'Manufacturer', 'ProductGroup']
 * };
 * </code></pre>
 * @extends YAHOO.ext.grid.LoadableDataModel
 * @constructor
*/
YAHOO.ext.grid.JSONDataModel = function(schema){
    YAHOO.ext.grid.JSONDataModel.superclass.constructor.call(this, YAHOO.ext.grid.LoadableDataModel.JSON);
    /**@private*/
    this.schema = schema;
};
YAHOO.extendX(YAHOO.ext.grid.JSONDataModel, YAHOO.ext.grid.LoadableDataModel);

/**
 * Overrides loadData in LoadableDataModel to process JSON data
 * @param {Object} data The JSON object to load
 * @param {Function} callback
 */
YAHOO.ext.grid.JSONDataModel.prototype.loadData = function(data, callback, keepExisting){
	var idField = this.schema.id;
	var fields = this.schema.fields;
	var rowData = [];
	try{
	    var root = eval('data.' + this.schema.root);
		for(var i = 0; i < root.length; i++){
			var node = root[i];
			var colData = [];
			colData.node = node;
			colData.id = node[idField] || String(i);
			for(var j = 0; j < fields.length; j++) {
			    var val = node[fields[j]] || "";
	            if(this.preprocessors[j]){
	                val = this.preprocessors[j](val);
	            }
	            colData.push(val);
	        }
	        rowData.push(colData);
		}
		if(keepExisting !== true){
		  this.removeAll();
		}
        this.addRows(rowData);
    	if(typeof callback == 'function'){
	    	callback(this, true);
	    }
    	this.fireLoadEvent();
	}catch(e){
		this.fireLoadException(e, null);
		if(typeof callback == 'function'){
	    	callback(this, false);
	    }
	}
};

/**
 * Overrides getRowId in DefaultDataModel to return the ID value of the specified node. 
 * @param {Number} rowIndex
 * @return {Number}
 */
YAHOO.ext.grid.JSONDataModel.prototype.getRowId = function(rowIndex){
    return this.data[rowIndex].id;
};