Using Platform Effector as One-Way collision callback ?

Hi guys,
I'd like to know if there is a clean way to get collision callbacks only when collision occurs in a specific direction.

I mean, it looks like platform effector 2D should do the trick but I haven't been able to achieve the expected results (maybe because I'm lame xD )

Anyway, how do you guys get your callbacks "direction selective" ?
I know that I could use if statements and check for positions and/or speed values but it seems kinda "hacky".
Thanks all !