Vavr: How to properly implement this?

[HiDAl]

Hello,

I would like got your advise on how to properly write this code on a functional way:

private Option<CalcResult> calculate(Integer X, Integer Y) {
  if (X < Y) return Option.none();
  return Option.of( X + Y );
} 

public Option<CalcResult> otherMethod(Obj o) {
  if (o.getAttr()) {
    // getA() & getB() are APIs out of my control and could return a null value
    if (o.getA() != null && o.getB() != null) {
      return calculate(o.getA(), o.getB());
    }
  } 

  return Option.none();
}

Calculate is simple:

private Option<CalcResult> calculate(Integer X, Integer Y) {
  return Option.when(X > Y, () -> X + Y);
} 

For otherMethod, This was my first approach:

public Option<CalcResult> otherMethod(Obj o) {
  return Option.when(o.getAttr(), () -> 
    For(Option.of(o.getA()), Option.of(o.getB()))
      .yield(this::calculate)
      .toOption()
      .flatMap(Function.identity())
    ).flatMap(Function.identity()); 
}

But, I feel the code is not as readable as I would expect, compared to first version (double flatMap makes hard to understand, at first sight, why is there)

I tried with this other, which improves the lecture:

public Option<CalcResult> otherMethod(Obj o) {
  return For(
      Option.when(o.getAttr(), o::getAttr()),
      Option.of(o.getA()), 
      Option.of(o.getB()))
    .yield((__, x, y) -> this.calculate(x, y))
    .toOption()
    .flatMap(Function.identity()); 
}

It's way more readable, but I think i'm not correctly using For-comprehension on this case.

What would be your recommendation on this case? am I correctly using vavr's API?

Thanks

[danieldietrich]

Please ask the question in our Gitter chat! We can't answer general questions here.
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Thx!

[nfekete]

Chat is ephemeral, so if you think your question might benefit others too, consider posting it on stackoverflow.

[HiDAl]

I asked it on stackoverflow: https://stackoverflow.com/questions/54113639/how-to-properly-implement-this-using-vavr

:)