source: Dev/trunk/src/client/dojox/grid/LazyTreeGridStoreModel.js

define([
        "dojo/_base/declare",
        "dojo/_base/array",
        "dojo/_base/lang",
        "dijit/tree/ForestStoreModel"], function(declare, array, lang, ForestStoreModel){

return declare("dojox.grid.LazyTreeGridStoreModel", ForestStoreModel, {

        // There are different approaches to get children for client-side
        // DataStore (e.g. dojo.data.ItemFileReadStore) or server-side DataStore
        // (e.g. dojox.data.QueryReadStore), so we need to be sure what kind of
        // DataStore is being used
        serverStore: false, // server side store
        
        constructor: function(/* Object */ args){
                this.serverStore = !!args.serverStore;
        },

        mayHaveChildren: function(/*dojo.data.Item*/ item){
                var children = null;
                return array.some(this.childrenAttrs, function(attr){
                                children = this.store.getValue(item, attr);
                                if(lang.isString(children)){
                                        return parseInt(children, 10) > 0 || children.toLowerCase() === "true" ? true : false;
                                }else if(typeof children == "number"){
                                        return children > 0;
                                }else if(typeof children == "boolean"){
                                        return children;
                                }else if(this.store.isItem(children)){
                                        children = this.store.getValues(item, attr);
                                        return lang.isArray(children) ? children.length > 0 : false;
                                }else{
                                        return false;
                                }
                }, this);
        },
        
        getChildren: function(/*dojo.data.Item*/parentItem, /*function(items, size)*/onComplete, /*function*/ onError, /*object*/queryObj){
                if(queryObj){
                        var start = queryObj.start || 0,
                                count = queryObj.count,
                                parentId = queryObj.parentId,
                                sort = queryObj.sort;
                        if(parentItem === this.root){
                                this.root.size = 0;
                                this.store.fetch({
                                        start: start,
                                        count: count,
                                        sort: sort,
                                        query: this.query,
                                        onBegin: lang.hitch(this, function(size){
                                                this.root.size = size;
                                        }),
                                        onComplete: lang.hitch(this, function(items){
                                                onComplete(items, queryObj, this.root.size);
                                        }),
                                        onError: onError
                                });
                        }else{
                                var store = this.store;
                                if(!store.isItemLoaded(parentItem)){
                                        var getChildren = lang.hitch(this, arguments.callee);
                                        store.loadItem({
                                                item: parentItem,
                                                onItem: function(parentItem){
                                                        getChildren(parentItem, onComplete, onError, queryObj);
                                                },
                                                onError: onError
                                        });
                                        return;
                                }
                                if(this.serverStore && !this._isChildrenLoaded(parentItem)){
                                        this.childrenSize = 0;
                                        this.store.fetch({
                                                start: start,
                                                count: count,
                                                sort: sort,
                                                query: lang.mixin({parentId: parentId}, this.query || {}),
                                                onBegin: lang.hitch(this, function(size){
                                                        this.childrenSize = size;
                                                }),
                                                onComplete: lang.hitch(this, function(items){
                                                        onComplete(items, queryObj, this.childrenSize);
                                                }),
                                                onError: onError
                                        });
                                }else{
                                        this.inherited(arguments);
                                }
                        }
                }else{
                        this.inherited(arguments);
                }
        },
        
        _isChildrenLoaded: function(parentItem){
                // summary:
                //              Check if all children of the given item have been loaded
                var children = null;
                return array.every(this.childrenAttrs, function(attr){
                        children = this.store.getValues(parentItem, attr);
                        return array.every(children, function(c){
                                return this.store.isItemLoaded(c);
                        }, this);
                }, this);
        },
        
        //overwritten
        onNewItem: function(item, parentInfo){ },
        
        onDeleteItem: function(item){ }
});
});