Data and Collections

Expose ViewModel's Properties

ViewModel, like a JavaBean, exposes its properties through getter and setter methods. Any property that VIew (ZUL) wants to retrieve through data binding should have a corresponding getter method. The method's return type can be primitive type (int, boolean...), or JavaBean. If a UI component needs to save its attribute value (it's usually user input) back to ViewModel's property, the ViewModel should provide a corresponding setter method. Therefore, through setter and getter any data change of both side (View & ViewModel) can be synchronized by data binding mechanism.

Property is Primitive Type

Primitive type property

public class PrimitiveViewModel{

	private int index;
	private double price;

	public int getIndex(){
		return index;
	}
	public void setIndex(int index){
		this.index = index;
	}

	public double getPrice(){
		return price;
	}
	public void setPrice(double price){
		this.price = price;
	}
	
}

A zul that uses PrimitiveViewModel

<window apply="org.zkoss.bind.BindComposer" viewModel="@id('vm') @init('foo.PrimitiveViewModel')" >

    <intbox value="@bind(vm.index)"/>

    <doublebox value="@bind(vm.price)"/>

    <!-- other components -->

</window>

• @id('vm') set ViewModel name, then we can use vm to reference ViewModel's property in the following components. (line 1)

Property is Object or JavaBean

If a property is a JavaBean, that JavaBean's property can also be accessed through EL expression.

Object type property

public class Address{
	private String city;
	private String street;

	//gettter & setter
}

public class ObjectViewModel{

	private Integer index;
	private String name;
	//JavaBean
	private Address address;

	public int getIndex(){
		return index;
	}
	public void setIndex(Integer index){
		this.index = index;
	}

	public String getName(){
		return name;
	}
	public void setName(String name){
		this.name = name;
	}

	public Item getAddress(){
		return address;
	}
	public void setAddress(Address address){
		this.address = address;
	}

}

A zul that uses ObjectViewModel.

    <intbox value="@bind(vm.index)"/>

    <textbox value="@load(vm.name)"/>

    <label value="@load(vm.address.street)"/>

• vm.address is a JavaBean, and we can access its property street with EL expression vm.address.street. (line 5)

Property is Collection

If the UI component is a collection container like listbox or grid, it should be bound to a property whose type is Map or subinterface of Collection like List or Set .

Collection type property

public class CollectionViewModel{
	//primitive type
	private int selectedIndex;
	//Collection
	private List itemList;

	public int getSelectedIndex(){
		return selectedIndex;
	}
	public void setSelectedIndex(int index){
		selectedIndex = index;
	}

	public List getItemList(){
		return itemList;
	}
}

• As we can't save whole list through data binding, the ViewModel only provide setter for itemList.

A zul that uses CollectionViewModel

    <label value="@load(vm.address.street)"/>
    <listbox model="@load(vm.itemList)" selectedIndex="@bind(vm.selectedIndex)">
        <!-- children of listbox -->
    </listbox>

• Listbox's model attribute should be bound to a collection object, vm.itemList. (line 4)

Version History

Version	Date	Content
6.0.0	February 2012	The MVVM was introduced.