[Swift-user] How can one force ordering into swift operations

[Lorenzo Pesce]

I have a simple problem:
step 1: I run an app that splits a file in a group of files and we don't know how many they are.
step2: I want to map those files using a mapper after the fact

Problem is that the mapper doesn't know that it can't run till step 1 is done because it has no input files. How can I tell the mapper (and what follows it by consequence since those files will not be there) that it has to wait for step 1 to b finished?

Thanks,

 Lorenzo