File: tree/js/plugins/tree-lazy.js
/*jshint expr:true, maxlen:200, onevar:false */
/**
Provides `Plugin.Tree.Lazy`, a plugin for `Tree.Openable` that makes it easy to
lazily load and populate the contents of tree nodes the first time they're
opened.
@module tree
@submodule tree-lazy
**/
/**
A plugin for `Tree.Openable` that makes it easy to lazily load and populate the
contents of tree nodes the first time they're opened.
### Example
YUI().use('jsonp', 'tree-openable', 'tree-lazy', function (Y) {
var Tree = Y.Base.create('openableTree', Y.Tree, [Y.Tree.Openable]),
tree = new Tree();
tree.plug(Y.Plugin.Tree.Lazy, {
// Custom function that Plugin.Tree.Lazy will call when it needs to
// load the children for a node.
load: function (node, callback) {
// Request the data for this node's children via JSONP.
Y.jsonp('http://example.com/api/data?callback={callback}', function (data) {
// If we didn't get any data back, treat this as an error.
if (!data) {
callback(new Error('No data!'));
return;
}
// Append the children to the node (assume `data.children` is
// an array of child node data for the sake of this example).
node.append(data.children);
// Call the callback function to tell Plugin.Tree.Lazy that
// we're done loading data.
callback();
});
}
});
});
@class Plugin.Tree.Lazy
@param {Object} config Config object.
@param {Function} config.load Custom `load()` function that will be called
when a node's children need to be loaded. This function must call the
provided callback to indicate completion.
@param {Function} config.load.callback Callback function. The custom
`load()` function must call this callback to indicate completion.
@param {Error} [config.load.callback.err] Error object. If provided,
the load action will be considered a failure, and an `error`
event will be fired. Omit this argument (or set it to `null`) to
indicate success.
@extends Plugin.Base
@constructor
**/
/**
Fired just before the custom `load()` method is called to load child nodes for a
node.
Calling `preventDefault()` on this event's facade will cancel the load action
and prevent the `load()` method from being called.
@event beforeLoad
@param {Tree.Node} node Tree node whose children will be loaded.
@preventable _defBeforeLoadFn
**/
var EVT_BEFORE_LOAD = 'beforeLoad';
/**
Fired when the `load()` method indicates there was an error loading child nodes.
@event error
@param {Error} error Error provided by the `load()` method.
@param {String} src Source of the error (defaults to "load").
**/
var EVT_ERROR = 'error';
/**
Fired after child nodes have finished loading and have been added to the tree.
@event load
@param {Tree.Node} node Tree node whose children have been loaded.
**/
var EVT_LOAD = 'load';
Y.namespace('Plugin.Tree').Lazy = Y.Base.create('lazyTreePlugin', Y.Plugin.Base, [], {
// -- Lifecycle Methods ----------------------------------------------------
initializer: function (config) {
this._host = config.host;
if (config.load) {
this.load = config.load;
}
// Make sure we've been plugged into a Tree that mixes in the
// Tree.Openable extension.
if (!this._host.openNode) {
Y.log("Plugin.Tree.Lazy was plugged into a Tree that doesn't mix in the Tree.Openable extension. This probably won't do you much good.", 'warn', 'tree-lazy');
}
this._published = {};
this._attachEvents();
},
// -- Public Methods -------------------------------------------------------
load: function (node, callback) {
callback(new Error('Plugin.Tree.Lazy: Please provide a custom `load` method when instantiating this plugin.'));
},
// -- Protected Methods ----------------------------------------------------
_attachEvents: function () {
this.onHostEvent('open', this._onOpen);
},
// -- Protected Event Handlers ---------------------------------------------
_onOpen: function (e) {
var node = e.node;
// Nothing to do if this node can't have children or if its children
// have already been (or are already being) loaded.
if (!node.canHaveChildren || node.state.loaded || node.state.loading) {
return;
}
if (!this._published[EVT_BEFORE_LOAD]) {
this._published[EVT_BEFORE_LOAD] = this.publish(EVT_BEFORE_LOAD, {
defaultFn: this._defLoadingFn
});
}
this.fire(EVT_BEFORE_LOAD, {node: node});
},
// -- Default Event Handlers -----------------------------------------------
_defLoadingFn: function (e) {
var node = e.node,
self = this;
node.state.loading = true;
this.load(node, function (err) {
delete node.state.loading;
if (err) {
self.fire(EVT_ERROR, {
error: err,
src : 'load'
});
return;
}
node.state.loaded = true;
self.fire(EVT_LOAD, {node: node});
});
}
}, {
NS: 'lazy'
});