I want to create an extension function to filter a list based on condition x, and if condition x ret...

# announcements

[xii]

I want to create an extension function to filter a list based on condition x, and if condition x returns an empty list, go for another condition, but I can't figure an idiomatic way to write it; here's what I've got:

[xii]

more specifically, I want to reuse part of the predicate is my concern

[xii]

private inline fun Iterable<TestObject>.emptyFilterIfNotContained(predicate: (TestObject) -> TestObject): List<TestObject>{
  return filterTo(ArrayList(), predicate).ifEmpty{ filterTo(ArrayList(), {it.b.isEmpty()}
}

but I want b to be variable, as in, be the object that the predicate just compared to

[xii]

so lets say I called that function with

test.emptyFilterIfNotContained { it.b.contains('a')}

then it should check for b,
but if I sent it.a.contains in the predicate, it should do it.a.isEmpty()

[Vlad]

assuming you are comparing string

private inline fun Iterable<TestObject>.emptyFilterIfNotContained(getValue:(TestObject)-> String, predicate: (String) -> Boolean): List<TestObject>{
    return filterTo(ArrayList()){predicate(getValue(it))}.ifEmpty { filterTo(ArrayList(), { getValue(it).isEmpty() })}
    }

and use like this

test.emptyFilterIfNotContained({it.a},{it.contains('a')})

[xii]

thats incredible

[xii]

thank you

[Marc Knaup]

Why do you use filterTo?