Question: how to create pch file?
Answer: From your Xcode menu, select File > New > File...
From iOS template options, select Other > PCH file.
Name the file <target_name>-Prefix. pch, and then select Create.
From your target's Build settings, select All, and then add the following to the Prefix Header field: $(SRCROOT)/<target_name>-Prefix.pch.