Children Binding

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 dynamically generated menuitems.

Steps to use this feature:

1. Create a List object as a ViewModel's property._[1]
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.

[1]: It must be a List object under CE edition.

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

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

Avaliable for ZK: EE

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 Data Binding/Converter