/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.user.client.ui;
import com.google.gwt.event.logical.shared.HasValueChangeHandlers;
import com.google.gwt.user.client.TakesValue;
/**
* Extends {@link TakesValue} to allow the value to be pulled back out, and to
* throw {@link com.google.gwt.event.logical.shared.ValueChangeEvent
* ValueChangeEvent} events.
* <p>
* An object that implements this interface should be a user input widget, where
* the user and programmer can both set and get the object's value. It is
* intended to provide a unified interface to widgets with "atomic" values, like
* Strings and Dates.
*
* @param <T> the type of value
*/
public interface HasValue<T> extends TakesValue<T>, HasValueChangeHandlers<T> {
/**
* Gets this object's value.
*
* @return the object's value
*/
T getValue();
/**
* Sets this object's value without firing any events. This should be
* identical to calling setValue(value, false).
* <p>
* It is acceptable to fail assertions or throw (documented) unchecked
* exceptions in response to bad values.
* <p>
* Widgets must accept null as a valid value. By convention, setting a widget to
* null clears value, calling getValue() on a cleared widget returns null. Widgets
* that can not be cleared (e.g. {@link CheckBox}) must find another valid meaning
* for null input.
*
* @param value the object's new value
*/
void setValue(T value);
/**
* Sets this object's value. Fires
* {@link com.google.gwt.event.logical.shared.ValueChangeEvent} when
* fireEvents is true and the new value does not equal the existing value.
* <p>
* It is acceptable to fail assertions or throw (documented) unchecked
* exceptions in response to bad values.
*
* @param value the object's new value
* @param fireEvents fire events if true and value is new
*/
void setValue(T value, boolean fireEvents);
}