how to fix build failed

on mac high sierra 10.13 ,xcode 9

Do you realise your question cannot be asked as you provide no information at all, except "it fails".

So please, when you post to the forum, take time to write a detailed description of the problem.

ok, on xcode ! when I try to launch the code from the button run (play ) then pop up come out (failed build) do you know how I can fix that?

Well, there is no enough information here. What are the error messages in the issue Navigator ?(the ! in a triangle)

Please provide detailed information if you really care to get any help.

while I'm tring to execute the code, not able to dispaly the output