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LazyLoadJSIStore.js
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LazyLoadJSIStore.js
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if(!dojo._hasResource["dojox.data.demos.stores.LazyLoadJSIStore"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
dojo._hasResource["dojox.data.demos.stores.LazyLoadJSIStore"] = true;
dojo.provide("dojox.data.demos.stores.LazyLoadJSIStore");
dojo.require("dojo.data.ItemFileReadStore");
dojo.declare("dojox.data.demos.stores.LazyLoadJSIStore", dojo.data.ItemFileReadStore, {
constructor: function(/* object */ keywordParameters){
// LazyLoadJSIStore extends ItemFileReadStore to implement an
// example of lazy-loading/faulting in items on-demand.
// Note this is certianly not a perfect implementation, it is
// an example.
},
isItemLoaded: function(/*object*/ item) {
// summary:
// Overload of the isItemLoaded function to look for items of type 'stub', which indicate
// the data hasn't been loaded in yet.
//
// item:
// The item to examine.
//For this store, if it has the value of stub for its type attribute,
//then the item basn't been fully loaded yet. It's just a placeholder.
if(this.getValue(item, "type") === "stub"){
return false;
}
return true;
},
loadItem: function(keywordArgs){
// summary:
// Overload of the loadItem function to fault in items. This assumes the data for an item is laid out
// in a RESTful sort of pattern name0/name1/data.json and so on and uses that to load the data.
// It will also detect stub items in the newly loaded item and insert the stubs into the ItemFileReadStore
// list so they can also be loaded in on-demand.
//
// item:
// The item to examine.
var item = keywordArgs.item;
this._assertIsItem(item);
//Build the path to the data.json for this item
//The path consists of where its parent was loaded from
//plus the item name.
var itemName = this.getValue(item, "name");
var parent = this.getValue(item, "parent");
var dataUrl = "";
if (parent){
dataUrl += (parent + "/");
}
//For this store, all child input data is loaded from a url that ends with data.json
dataUrl += itemName + "/data.json";
//Need a reference to the store to call back to its structures.
var self = this;
// Callback for handling a successful load.
var gotData = function(data){
//Now we need to modify the existing item a bit to take it out of stub state
//Since we extend the store and have knowledge of the internal
//structure, this can be done here. Now, is we extended
//a write store, we could call the write APIs to do this too
//But for a simple demo the diretc modification in the store function
//is sufficient.
//Clear off the stub indicators.
delete item.type;
delete item.parent;
//Set up the loaded values in the format ItemFileReadStore uses for attributes.
for (i in data) {
if (dojo.isArray(data[i])) {
item[i] = data[i];
}else{
item[i] = [data[i]];
}
}
//Reset the item in the reference.
self._arrayOfAllItems[item[self._itemNumPropName]] = item;
//Scan the new values in the item for extra stub items we need to
//add to the items array of the store so they can be lazy-loaded later...
var attributes = self.getAttributes(item);
for(i in attributes){
var values = self.getValues(item, attributes[i]);
for (var j = 0; j < values.length; j++) {
var value = values[j];
if(typeof value === "object"){
if(value["stub"] ){
//We have a stub reference here, we need to create the stub item
var stub = {
type: ["stub"],
name: [value["stub"]], //
parent: [itemName] //The child stub item is parented by this item name...
};
if (parent) {
//Add in any parents to your parent so URL construstruction is accurate.
stub.parent[0] = parent + "/" + stub.parent[0];
}
//Finalize the addition of the new stub item into the ItemFileReadStore list.
self._arrayOfAllItems.push(stub);
stub[self._storeRefPropName] = self;
stub[self._itemNumPropName] = (self._arrayOfAllItems.length - 1); //Last one pushed in should be the item
values[j] = stub; //Set the stub item back in its place and replace the stub notation.
}
}
}
}
//Done processing! Call the onItem, if any.
if(keywordArgs.onItem){
var scope = keywordArgs.scope ? keywordArgs.scope : dojo.global;
keywordArgs.onItem.call(scope, item);
}
};
//Callback for any errors that occur during load.
var gotError = function(error){
//Call the onComplete, if any
if(keywordArgs.onError){
var scope = keywordArgs.scope ? keywordArgs.scope : dojo.global;
keywordArgs.onError.call(scope, error);
}
};
//Fire the get and pass the proper callbacks to the deferred.
var xhrArgs = {
url: dataUrl,
handleAs: "json-comment-optional"
};
var d = dojo.xhrGet(xhrArgs);
d.addCallback(gotData);
d.addErrback(gotError);
}
});
}

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