Children Binding

This article is out of date, please refer to zk-mvvm-book/8.0/data_binding/children_binding for more up to date information.

Create Children Dynamically with Template

Children binding allows us to bind child components to a collection then we can create a group of similar components dynamically upon the collection with <template>. Typically we also can do this by listbox or grid, but they have fixed structure and layout. With this feature we can create child components more flexible, like: a group of checkbox that options comes from a list, or dynamic generated menuitems.

Steps to use this feature:

1. Create a List object as a ViewModel's property.
2. Bind a parent component's children attribute with @init or @load to the ViewModel's property
3. Use <template> to enclose child components and set its name attribute to children. Because children binding chooses the default template with name children.

Basic usage example

<window apply="org.zkoss.bind.BindComposer" viewModel="@id('vm') @init('foo.ChildrenSimpleVM')">
	Simple - Init
	<vlayout id="init" children="@init(vm.nodes)">
		<template name="children" var="node">
			<label value="@bind(node.name)" style="padding-left:10px"/>
		</template>
	</vlayout> 
	Simple - load
	<vlayout id="load" children="@load(vm.nodes)">
		<template name="children" var="node">
			<label value="@bind(node.name)" style="padding-left:10px"/>
		</template>
	</vlayout>
	Simple - load after cmd
	<vlayout id="aftercmd" children="@load(vm.nodes, after='cmd')">
		<template name="children" var="node">
			<label value="@bind(node.name)" style="padding-left:10px"/>
		</template>
	</vlayout>
	<!-- other components -->
</window>

Basic usage screenshot

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Combine with Dynamic Template

If you combine this feature with dynamic template, you can even render different child components upon different conditions.

Here is an example to create a dynamic menu bar. If a menu item has no sub-menu, we use menuitem otherwise we use menu.

An example of dynamic menu bar

 
	<menubar id="mbar" children="@bind(vm.nodes) @template(empty each.children?'menuitem':'menu')">
		<template name="menu" var="node">
			<menu label="@bind(node.name)">
				<menupopup children="@bind(node.children) @template(empty each.children?'menuitem':'menu')"/>
			</menu>
		</template>
		<template name="menuitem" var="node">
			<menuitem label="@bind(node.name)" onClick="@command('menuClicked',node=node)" />
		</template>
	</menubar>

Dynamic menu bar screenshot

Default Converter for Children Binding

• Available for ZK:
• 

Since 6.0.1

Users usually bind attribute "children" to a Collection object, but you can also bind it to a Array, Enum, even an Object. An implicit default converter will convert them to a Collection object. Certainly, you can apply your customized converter and we will talk about it at ZK Developer's Reference/MVVM/Data Binding/Converter

Version History

Version	Date	Content
6.0.0	February 2012	The MVVM was introduced.