org.apache.wicket.markup.html.form

Class ChoiceRenderer<T>

java.lang.Object

org.apache.wicket.markup.html.form.ChoiceRenderer<T>

Type Parameters:

T - The model object type

All Implemented Interfaces:

Serializable, IChoiceRenderer<T>, IClusterable

Direct Known Subclasses:

EnumChoiceRenderer

public class ChoiceRenderer<T>
extends Object
implements IChoiceRenderer<T>, IClusterable

Renders one choice. Separates the 'id' values used for internal representation from 'display values' which are the values shown to the user of components that use this renderer. Usage:

 new DropDownChoice<User>("users", new Model<User>(selectedUser), listOfUsers)
 

creates a DropDownChoice of users and the display value will be toString() and the id the index of the object in the ListOfUsers.

 new DropDownChoice<User>("users", new Model<User>(selectedUser), listOfUsers,
        new ChoiceRenderer<User>("name"))
 

creates a DropDownChoice of users and the display value will be looked up by property expression ("name") and the id the index of the object in the ListOfUsers

 new DropDownChoice<User>("users", new Model<User>(selectedUser), listOfUsers,
        new ChoiceRenderer<User>("name", "id"))
 

creates a DropDownChoice of users and the display value will be looked up by property expression ("name") and the id will be looked up by the property expression "id"

Author:

jcompagner

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ChoiceRenderer() Constructor.
ChoiceRenderer(String displayExpression) Constructor.
ChoiceRenderer(String displayExpression, String idExpression) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
Object	getDisplayValue(T object) Get the value for displaying to an end user.
String	getIdValue(T object, int index) This method is called to get the id value of an object (used as the value attribute of a choice element) The id can be extracted from the object like a primary key, or if the list is stable you could just return a toString of the index.
T	getObject(String id, IModel<? extends List<? extends T>> choices) This method is called to get an object back from its id representation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ChoiceRenderer

public ChoiceRenderer()

Constructor. When you use this constructor, the display value will be determined by calling toString() on the list object, and the id will be based on the list index. the id value will be the index

ChoiceRenderer

public ChoiceRenderer(String displayExpression)

Constructor. When you use this constructor, the display value will be determined by executing the given property expression on the list object, and the id will be based on the list index. The display value will be calculated by the given property expression

Parameters:

displayExpression - A property expression to get the display value

ChoiceRenderer

public ChoiceRenderer(String displayExpression,
              String idExpression)

Constructor. When you use this constructor, both the id and the display value will be determined by executing the given property expressions on the list object.

Parameters:

displayExpression - A property expression to get the display value

idExpression - A property expression to get the id value

Method Detail

getDisplayValue

public Object getDisplayValue(T object)

Description copied from interface: IChoiceRenderer

Get the value for displaying to an end user.

Specified by:

getDisplayValue in interface IChoiceRenderer<T>

Parameters:

object - the actual object

Returns:

the value meant for displaying to an end user

getIdValue

public String getIdValue(T object,
                int index)

Description copied from interface: IChoiceRenderer

This method is called to get the id value of an object (used as the value attribute of a choice element) The id can be extracted from the object like a primary key, or if the list is stable you could just return a toString of the index.

Note that the given index can be -1 if the object in question is not contained in the available choices.

Specified by:

getIdValue in interface IChoiceRenderer<T>

Parameters:

object - The object for which the id should be generated

index - The index of the object in the choices list.

Returns:

String

getObject

public T getObject(String id,
          IModel<? extends List<? extends T>> choices)

Description copied from interface: IChoiceRenderer

This method is called to get an object back from its id representation. The id may be used to find/load the object in a more efficient way than loading all choices and find the one with the same id in the list

Specified by:

getObject in interface IChoiceRenderer<T>

Parameters:

id - The id representation of the object

choices - The list of all rendered choices

Returns:

A choice from the list that has this id