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package javafx.beans.binding;

import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;


A Binding calculates a value that depends on one or more sources. The sources are usually called the dependency of a binding. A binding observes its dependencies for changes and updates its value automatically. 
 While a dependency of a binding can be anything, it is almost always an implementation of ObservableValue. Binding implements ObservableValue allowing to use it in another binding. With that one can assemble very complex bindings from simple bindings. 

All bindings in the JavaFX runtime are calculated lazily. That means, if
a dependency changes, the result of a binding is not immediately
recalculated, but it is marked as invalid. Next time the value of an invalid
binding is requested, it is recalculated.

 It is recommended to use one of the base classes defined in this package (e.g. DoubleBinding) to define a custom binding, because these classes already provide most of the needed functionality. See DoubleBinding for an example. 
Type parameters:
  • <T> – the type of the wrapped value
See Also:
Since:JavaFX 2.0
/**
 * A {@code Binding} calculates a value that depends on one or more sources. The
 * sources are usually called the dependency of a binding. A binding observes
 * its dependencies for changes and updates its value automatically.
 * <p>
 * While a dependency of a binding can be anything, it is almost always an
 * implementation of {@link javafx.beans.value.ObservableValue}. {@code Binding}
 * implements {@code ObservableValue} allowing to use it in another binding.
 * With that one can assemble very complex bindings from simple bindings.
 * <p>
 * All bindings in the JavaFX runtime are calculated lazily. That means, if
 * a dependency changes, the result of a binding is not immediately
 * recalculated, but it is marked as invalid. Next time the value of an invalid
 * binding is requested, it is recalculated.
 * <p>
 * It is recommended to use one of the base classes defined in this package
 * (e.g. {@link DoubleBinding}) to define a custom binding, because these
 * classes already provide most of the needed functionality. See
 * {@link DoubleBinding} for an example.
 *
 * @param <T> the type of the wrapped value
 * @see DoubleBinding
 *
 * @since JavaFX 2.0
 */
public interface Binding<T> extends ObservableValue<T> {

    
Checks if a binding is valid.

Returns:true if the Binding is valid, false otherwise
/**
     * Checks if a binding is valid.
     *
     * @return {@code true} if the {@code Binding} is valid, {@code false}
     *         otherwise
     */
    boolean isValid();

    
Mark a binding as invalid. This forces the recalculation of the value of the Binding next time it is request. 
/**
     * Mark a binding as invalid. This forces the recalculation of the value of
     * the {@code Binding} next time it is request.
     */
    void invalidate();

    
Returns the dependencies of a binding in an unmodifiable ObservableList. The implementation is optional. The main purpose of this method is to support developers during development. It allows to explore and monitor dependencies of a binding during runtime. 
 Because this method should not be used in production code, it is recommended to implement this functionality as sparse as possible. For example if the dependencies do not change, each call can generate a new ObservableList, avoiding the necessity to store the result. 
Returns:an unmodifiable  ObservableList of the dependencies
/**
     * Returns the dependencies of a binding in an unmodifiable
     * {@link javafx.collections.ObservableList}. The implementation is
     * optional. The main purpose of this method is to support developers during
     * development. It allows to explore and monitor dependencies of a binding
     * during runtime.
     * <p>
     * Because this method should not be used in production code, it is
     * recommended to implement this functionality as sparse as possible. For
     * example if the dependencies do not change, each call can generate a new
     * {@code ObservableList}, avoiding the necessity to store the result.
     *
     * @return an unmodifiable {@code} ObservableList of the dependencies
     */
    ObservableList<?> getDependencies();

    
Signals to the Binding that it will not be used anymore and any references can be removed. A call of this method usually results in the binding stopping to observe its dependencies by unregistering its listener(s). The implementation is optional. 
 All bindings in our implementation use instances of WeakInvalidationListener, which means usually a binding does not need to be disposed. But if you plan to use your application in environments that do not support WeakReferences you have to dispose unused Bindings to avoid memory leaks. 
/**
     * Signals to the {@code Binding} that it will not be used anymore and any
     * references can be removed. A call of this method usually results in the
     * binding stopping to observe its dependencies by unregistering its
     * listener(s). The implementation is optional.
     * <p>
     * All bindings in our implementation use instances of
     * {@link javafx.beans.WeakInvalidationListener}, which means usually
     * a binding does not need to be disposed. But if you plan to use your
     * application in environments that do not support {@code WeakReferences}
     * you have to dispose unused {@code Bindings} to avoid memory leaks.
     */
    void dispose();

}