Module org.apache.wicket.core
Package 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>, IDetachable, IClusterable
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:

  • Constructor Details

    • 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 Details

    • 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