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## com.jgoodies.binding.value
Class AbstractVetoableValueModel

    java.lang.Object
      com.jgoodies.common.bean.Bean
          com.jgoodies.binding.beans.Model
              com.jgoodies.binding.value.AbstractValueModel
                  com.jgoodies.binding.value.AbstractVetoableValueModel

All Implemented Interfaces:
  ValueModel, com.jgoodies.common.bean.ObservableBean, com.jgoodies.common.bean.ObservableBean2, Serializable

    public abstract class AbstractVetoableValueModel

extends AbstractValueModel

A ValueModel that allows to accept or reject proposed value changes. Useful to request information from the user or to perform operations before a value is changed.

Wraps a given subject ValueModel and always returns the subject value as this model's value. Observes subject value changes and forwards them to listeners of this model. If a value is set to this model, the abstract method `#proposedChange` is invoked. In this method implementors define how to accept or reject value changes.

Implementors may veto against a proposed change based on the application state or by asking the user, and may also perform additional operations during the check, for example to save editor contents. Here's an example:

     public class CheckPendingEditValueModel extends AbstractVetoableValueModel {

         public CheckPendingEditValueModel(ValueModel subject) {
             super(subject);
         }

         public boolean proposedChange(Object oldValue, Object proposedNewValue) {
             if (equals(oldValue, proposedNewValue))
                 return true;
             int option = JOptionPane.showConfirmDialog(
                 Application.getDefaultParentFrame(),
                 "Do you want to save the editor contents.");
             if (option == JOptionPane.YES_OPTION)
                 model.save();
             return option != JOptionPane.CANCEL_OPTION;
         }
     }

Since:
  1.1
Version:
  $Revision: 1.12 $
Author:
  Karsten Lentzsch
See Also:
  Serialized Form

Field Summary

Fields inherited from class com.jgoodies.common.bean.Bean
`changeSupport`

Fields inherited from interface com.jgoodies.binding.value.ValueModel
`PROPERTY_VALUE`

Constructor Summary
`protected` | `AbstractVetoableValueModel(ValueModel subject)` Constructs an AbstractVetoableValueModel for the given ValueModel.

Method Summary
`Object` | `getValue()` Returns this model's current subject value.
`abstract boolean` | `proposedChange(Object oldValue, Object proposedNewValue)` Checks and answers whether the proposed value change shall be accepted or rejected.
`void` | `setValue(Object newValue)` Sets the given value as new subject value if and only if 1) the new value differs from the old value and 2) the proposed change is accepted as checked by `proposedChange(oldValue, newValue)`.

Methods inherited from class com.jgoodies.binding.value.AbstractValueModel
`addValueChangeListener, booleanValue, doubleValue, fireValueChange, fireValueChange, fireValueChange, fireValueChange, fireValueChange, fireValueChange, fireValueChange, floatValue, getString, intValue, longValue, paramString, removeValueChangeListener, setValue, setValue, setValue, setValue, setValue, toString, valueString`

Methods inherited from class com.jgoodies.binding.beans.Model
`createPropertyChangeSupport, firePropertyChange`

Methods inherited from class com.jgoodies.common.bean.Bean
`addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, addVetoableChangeListener, fireIndexedPropertyChange, fireIndexedPropertyChange, fireIndexedPropertyChange, fireMultiplePropertiesChanged, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, getPropertyChangeListeners, getPropertyChangeListeners, getVetoableChangeListeners, getVetoableChangeListeners, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, removeVetoableChangeListener`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### AbstractVetoableValueModel

    protected AbstractVetoableValueModel(ValueModel subject)

  Constructs an AbstractVetoableValueModel for the given ValueModel.

  Parameters:
    `subject` - the underlying (or wrapped) ValueModel
  Throws:
    `NullPointerException` - if the subject is `null`

Method Detail

### proposedChange

    public abstract boolean proposedChange(Object oldValue,
                                           Object proposedNewValue)

  Checks and answers whether the proposed value change shall be accepted or rejected. Implementors may perform additional operations, for example to save a pending editor content.

  Parameters:
    `oldValue` - the value before the change
    `proposedNewValue` - the new value if the change is accepted
  Returns:
    true to accept the proposed value, false to veto against it.

### getValue

    public final Object getValue()

  Returns this model's current subject value.

  Returns:
    this model's current subject value.

### setValue

    public final void setValue(Object newValue)

  Sets the given value as new subject value if and only if 1) the new value differs from the old value and 2) the proposed change is accepted as checked by `proposedChange(oldValue, newValue)`.

  Parameters:
    `newValue` - the value to set

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