ObservableCondition

gistfile1.groovy

/**
 * Observes an {@link Observable<T>} and returns a new Observable<R> that emits
 * items based on the predicate<T> and the <R> onTrue and <R> onFalse functions.
 */
public class ObservableCondition<R, T> {
    private final rx.Observable<T> condition;
    private Func0<? extends R> onTrue = {}
    private Func0<? extends R> onFalse = {}
    private Predicate<T> predicate;

    private def ofBoolean = new Predicate<Boolean>() {
        @Override
        boolean apply(Boolean inp) {
            inp.booleanValue()
        }
    }

    ObservableCondition(rx.Observable<T> condition) {
        this.condition = condition
        this.predicate = ofBoolean
    }

    ObservableCondition(rx.Observable<T> condition, Predicate<T> predicate) {
        this.condition = condition
        this.predicate = predicate
    }

    public ObservableCondition onTrue(final Func0<? extends R> onTrue) {
        this.onTrue = onTrue
        this
    }

    public ObservableCondition onFalse(final Func0<? extends R> onFalse) {
        this.onFalse = onFalse
        this
    }

    public ObservableCondition predicate(Predicate<?> predicate) {
        this.predicate = predicate
        this
    }

    public rx.Observable<R> build() {
        condition.map(predicateFn(predicate, onTrue, onFalse))
    }

    private static <T> Func1<T, ? extends R> predicateFn(Predicate<T> predicate,
                                                         Func0<? extends R> onTrue,
                                                         Func0<? extends R> onFalse) {
        { T inp ->
            if(predicate.apply(inp)) {
                onTrue()
            } else {
                onFalse()
            }
        }
    }
}