Class MultiValidator


  • public abstract class MultiValidator
    extends ValidationStatusProvider
    A validator for cross-constraints between observables.

    Some practical examples of cross-constraints:

    • A start date cannot be later than an end date
    • A list of percentages should add up to 100%

    Example: require two integer fields to contain either both even or both odd numbers.

     DataBindingContext dbc = new DataBindingContext();
    
     IObservableValue target0 = SWTObservables.observeText(text0, SWT.Modify);
     IObservableValue target1 = SWTObservables.observeText(text1, SWT.Modify);
    
     // Binding in two stages (from target to middle, then from middle to model)
     // simplifies the validation logic.  Using the middle observables saves
     // the trouble of converting the target values (Strings) to the model type
     // (integers) manually during validation.
     final IObservableValue middle0 = new WritableValue(null, Integer.TYPE);
     final IObservableValue middle1 = new WritableValue(null, Integer.TYPE);
     dbc.bind(target0, middle0, null, null);
     dbc.bind(target1, middle1, null, null);
    
     // Create the multi-validator
     MultiValidator validator = new MultiValidator() {
            protected IStatus validate() {
                    // Calculate the validation status
                    Integer value0 = (Integer) middle0.getValue();
                    Integer value1 = (Integer) middle1.getValue();
                    if (Math.abs(value0.intValue()) % 2 != Math.abs(value1.intValue()) % 2)
                            return ValidationStatus
                                            .error("Values must be both even or both odd");
                    return ValidationStatus.ok();
            }
     };
     dbc.addValidationStatusProvider(validator);
    
     // Bind the middle observables to the model observables.
     IObservableValue model0 = new WritableValue(Integer.valueOf(2), Integer.TYPE);
     IObservableValue model1 = new WritableValue(Integer.valueOf(4), Integer.TYPE);
     dbc.bind(middle0, model0, null, null);
     dbc.bind(middle1, model1, null, null);
     

    MultiValidator can also prevent invalid data from being copied to model. This is done by wrapping each target observable in a validated observable, and then binding the validated observable to the model.

    
     ...
    
     // Validated observables do not change value until the validator passes.
     IObservableValue validated0 = validator.observeValidatedValue(middle0);
     IObservableValue validated1 = validator.observeValidatedValue(middle1);
     IObservableValue model0 = new WritableValue(Integer.valueOf(2), Integer.TYPE);
     IObservableValue model1 = new WritableValue(Integer.valueOf(4), Integer.TYPE);
     // Bind to the validated value, not the middle/target
     dbc.bind(validated0, model0, null, null);
     dbc.bind(validated1, model1, null, null);
     
    Note: No guarantee is made as to the order of updates when multiple validated observables change value at once (i.e. multiple updates pending when the status becomes valid). Therefore the model may be in an invalid state after the first but before the last pending update.
    Since:
    1.1
    • Constructor Detail

      • MultiValidator

        public MultiValidator()
        Constructs a MultiValidator on the default realm.
      • MultiValidator

        public MultiValidator​(Realm realm)
        Constructs a MultiValidator on the given realm.
        Parameters:
        realm - the realm on which validation takes place.
    • Method Detail

      • revalidate

        protected final void revalidate()
        Signals that a re-evaluation of the current validation status is necessary.

        Clients may invoke this method whenever the validation status needs to be updated due to some state change which cannot be automatically tracked by the MultiValidator as it is not captured by any IObservable instance.

        Note: There is no guarantee as of whether the MultiValidator will immediately re-evaluate the validation status by calling validate() when becoming dirty. Instead, it may decide to perform the re-evaluation lazily.

        Since:
        1.2
        See Also:
        validate()
      • validate

        protected abstract IStatus validate()
        Returns the current validation status.

        Note: To ensure that the validation status is kept current automatically, all dependencies used to calculate status should be accessed through IObservable instances. Each dependency observable must be in the same realm as the MultiValidator. Other dependencies not captured by the state of those observables may be accounted for by having clients explicitly call revalidate() whenever the validation status needs to be re-evaluated due to some arbitrary change in the application state.

        Returns:
        the current validation status.
        See Also:
        revalidate()
      • observeValidatedValue

        public <T> IObservableValue<T> observeValidatedValue​(IObservableValue<T> target)
        Returns a wrapper IObservableValue which stays in sync with the given target observable only when the validation status is valid. Statuses of OK, INFO or WARNING severity are considered valid.

        The wrapper behaves as follows with respect to the validation status:

        • While valid, the wrapper stays in sync with its target observable.
        • While invalid, the wrapper's value is the target observable's last valid value. If the target changes value, a stale event is fired signaling that a change is pending.
        • When status changes from invalid to valid, the wrapper takes the value of the target observable, and synchronization resumes.
        Parameters:
        target - the target observable being wrapped. Must be in the same realm as the MultiValidator.
        Returns:
        an IObservableValue which stays in sync with the given target observable only with the validation status is valid.
      • observeValidatedList

        public <E> IObservableList<E> observeValidatedList​(IObservableList<E> target)
        Returns a wrapper IObservableList which stays in sync with the given target observable only when the validation status is valid. Statuses of OK, INFO or WARNING severity are considered valid.

        The wrapper behaves as follows with respect to the validation status:

        • While valid, the wrapper stays in sync with its target observable.
        • While invalid, the wrapper's elements are the target observable's last valid elements. If the target changes elements, a stale event is fired signaling that a change is pending.
        • When status changes from invalid to valid, the wrapper takes the elements of the target observable, and synchronization resumes.
        Parameters:
        target - the target observable being wrapped. Must be in the same realm as the MultiValidator.
        Returns:
        an IObservableValue which stays in sync with the given target observable only with the validation status is valid.
      • observeValidatedSet

        public <E> IObservableSet<E> observeValidatedSet​(IObservableSet<E> target)
        Returns a wrapper IObservableSet which stays in sync with the given target observable only when the validation status is valid. Statuses of OK, INFO or WARNING severity are considered valid.

        The wrapper behaves as follows with respect to the validation status:

        • While valid, the wrapper stays in sync with its target observable.
        • While invalid, the wrapper's elements are the target observable's last valid elements. If the target changes elements, a stale event is fired signaling that a change is pending.
        • When status changes from invalid to valid, the wrapper takes the elements of the target observable, and synchronization resumes.
        Parameters:
        target - the target observable being wrapped. Must be in the same realm as the MultiValidator.
        Returns:
        an IObservableValue which stays in sync with the given target observable only with the validation status is valid.
      • observeValidatedMap

        public <K,​V> IObservableMap<K,​V> observeValidatedMap​(IObservableMap<K,​V> target)
        Returns a wrapper IObservableMap which stays in sync with the given target observable only when the validation status is valid. Statuses of OK, INFO or WARNING severity are considered valid.

        The wrapper behaves as follows with respect to the validation status:

        • While valid, the wrapper stays in sync with its target observable.
        • While invalid, the wrapper's entries are the target observable's last valid entries. If the target changes entries, a stale event is fired signaling that a change is pending.
        • When status changes from invalid to valid, the wrapper takes the entries of the target observable, and synchronization resumes.
        Parameters:
        target - the target observable being wrapped. Must be in the same realm as the MultiValidator.
        Returns:
        an IObservableValue which stays in sync with the given target observable only with the validation status is valid.