In Xcode, how to suppress all warnings in specific source files?

Select Project in left navigator and select target go to build phase and Put -w in Build Phase of target file. It will hide all compiler warnings

Select your target and show Build Phases. Then enter the name of the file in the search box, and you should see it listed in the Compile Sources phase. Double-click in the Compiler Flags column for that file and enter -w to turn off all warnings for that file.

This works for Xcode 10.2+ and Swift 5

Manual fix:

Add -w -Xanalyzer -analyzer-disable-all-checks to the problematic file from Xcode > Project > Targets > Compile Sources > Double click the file where you want to turn off warnings.

Cocoapods Fix:

If you're trying to suppress warnings from a problematic pod, you can automatically suppress all warnings from the dependency with the inhibit_warnings flag in your podfile:

pod 'Kingfisher', '~> 4.6', :inhibit_warnings => true