Conditional Observable stuff

gistfile1.groovy

// First sketch, with just functions.
// Usage:
// Observable<Boolean> myCondition = ...
// Observable<List<Foo>> foos = onCondition(myCondition,
//      fetchFoos(a1, a2, a3),  // returns a Func0<Observable<List<Foo>>>
//     { empty() })
//    .flatMap({it})
public final static <R> Observable<R> onCondition(Observable<Boolean> observable,
                                                      final Func0<? extends R> onTrue,
                                                      final Func0<? extends R> onFalse) {
  observable.map(conditionalFn(onTrue, onFalse))
}

static def <R> Func1<? super Boolean, ? extends R> conditionalFn(Func0<? extends R> onTrue, Func0<? extends R> onFalse) {
  { boolean condition ->
    if(condition) {
      onTrue()
    } else {
      onFalse()
    }
  }
}

public final static <R> Observable<R> onCondition(Observable<Boolean> observable, final Func0<? extends R> onTrue) {
  observable.map(conditionalFn(onTrue))
}

static def <R> Func1<? super Boolean, ? extends R> conditionalFn(Func0<? extends R> onTrue) {
  { boolean condition ->
    if(condition) {
      onTrue()
    }
  }
}


// Second sketch with class instead
// Usage:
// Observable<Boolean> myCondition = ...
// Observable<List<Foo>> foos = new ConditionalObs<>(myCondition)
//                .onTrue(fetchFoos(a1, a2, a3))
//                .onFalse( { empty() })
//                .build()
//                .flatMap({it})
public class ConditionalObs<R> {
  private final Observable<Boolean> condition
  private Func0<? extends R> onTrue = {}
  private Func0<? extends R> onFalse = {}

  ConditionalObs(Observable<Boolean> condition) {
    this.condition = condition
  }

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

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

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

  private Func1<? super Boolean, ? extends R> conditionalFn(Func0<? extends R> onTrue, Func0<? extends R> onFalse) {
    { boolean condition ->
      if(condition) {
        onTrue()
      } else {
        onFalse()
      }
    }
  }
}