Dojo: The Definitive Guide

Parent-Child Relationships with _Container and _Contained

After you've been rolling with _Widget and _Templated for a while, it won't be long before you find that it's convenient to have a widget that contains some children widgets. The "has-a relationship" pattern is quite common in programming and it is no different with Dojo. The _Container and _Contained mixins are designed to facilitate the referencing back and forth between parents and children that often needs to happen. Table 12-1 summarizes the API.

Table 12-1. _Container and _Contained mixins

Name	Comment
removeChild(/*Object*/ dijit)	Removes the child widget from the parent. (Silently fails if the widget is not a child or if the container does not have any children.)
addChild(/*Object*/ dijit, /*Integer?*/ insertIndex)	Adds a child widget to the parent, optionally using the insertIndex to place it.
getParent( )	Allows a child to reference its parent. Returns a dijit instance.
getChildren( )	Allows a parent to conveniently enumerate each of its children dijits. Returns an Array of dijit instances.
getPreviousSibling( )	Allows a child widget to reference its previous sibling, i.e., the one "to the left." Returns a dijit instance.
getNextSibling( )	Allows a child widget to reference its next sibling, i.e., the one "to the right." Returns a dijit instance.

You'll see these mixins used extensively when you learn about the layout dijits. Next, we'll look at an example.