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Provides simple observable properties with binding capabilities.
/*
* Copyright 2017 Johannes Donath
* and other copyright owners as documented in the project's IP log.
*
* 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.torchmind.observable.binding;
import com.torchmind.observable.ReadOnlyObservable;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.function.BiPredicate;
import java.util.function.BooleanSupplier;
import java.util.function.Function;
import java.util.function.Supplier;
import javax.annotation.Nonnull;
/**
* Provides a generic binding which may be used in order to define property values based on more
* complex logic and expressions.
*
* @author Johannes Donath
*/
public interface Binding extends ReadOnlyObservable {
/**
* Creates a binding using the passed supplier and list of dependencies.
*
* Note that this method requires manual implementation of the respective binding logic. For
* most cases, however, the static methods provided by this interface do suffice however and
* require far less manually programmed logic.
*/
@Nonnull
static Binding create(@Nonnull Supplier supplier,
ReadOnlyObservable... observables) {
return new AbstractBinding(new HashSet<>(Arrays.asList(observables))) {
@Override
protected V compute() {
return supplier.get();
}
};
}
/**
* Maps an original value to another using complex logic.
*
* Note that the provided mapping function must be null-safe as no attempts will be made to
* strip or special case null values provided by the supplied observable.
*/
@Nonnull
static Binding map(@Nonnull Function function,
@Nonnull ReadOnlyObservable observable) {
return create(() -> function.apply(observable.get()), observable);
}
/**
* Creates a binding which is equal in functionality to the ternary operator (e.g. when the
* predicate evaluates to true, the first observable value is returned, otherwise the second is
* returned).
*/
@Nonnull
static Binding ternary(@Nonnull BiPredicate predicate,
@Nonnull ReadOnlyObservable observable1,
@Nonnull ReadOnlyObservable observable2) {
return create(() -> {
V value1 = observable1.get();
V value2 = observable2.get();
return predicate.test(value1, value2) ? value1 : value2;
}, observable1, observable2);
}
/**
* Creates a binding which is equal in functionality to the ternary operator (e.g. when the
* supplier evaluates to true, the first value is returned, otherwise the second is returned).
*/
@Nonnull
static Binding ternary(@Nonnull BooleanSupplier supplier, V value1, V value2) {
return create(() -> supplier.getAsBoolean() ? value1 : value2);
}
/**
* Converts the logic of this binding into a standard Java supplier.
*/
@Nonnull
Supplier asSupplier();
/**
* Retrieves a list of observables that this binding relies upon.
*/
@Nonnull
Set> getDependencies();
/**
* Forces this binding to re-evaluate its state based on the properties of its dependencies.
*/
void invalidate();
}