Error: Could not build Objective-C module 'Firebase'

Question

There is only one way to solve this issue.

1. Quit Xcode.
2. Delete project's temp files located at ~/Library/Developer/Xcode/DerivedData
3. Delete ProjectName.xcworkspace
4. Delete Podfile.lock file and Pods folder
5. Run pod install.
6. Open the newly created ProjectName.xcworkspace file and build.

Build (⌘ + B) worked for me.

I am using Swift 4 and Xcode 9. All I have to do is selecting FirebaseCore Scheme.

On Xcode:

Product->Scheme->FirebaseCore.

If you don't have FirebaseCore go to Manage Schemes and select it. Then try again.

This may fix your problem:

1. Quit the Xcode. (Don't just close the Xcode window, right click and Quit it explicitly).

2. Go to ~/Library/Developer/Xcode/DerivedData and delete the project folder. (Simply delete all the folders).

3. Clean and Build the project.

If still error exist:

Do steps 1 and 2 and follow this steps:

4. Change scheme to Firebase and Build (Command + B).

5. Change back to your app scheme and Run again.

I opened the project with .xcodeproj and I installed Firebase with cocoapods. I got the same error. But I just close the project and open it with .xcworkspace.

The alert has gone. Firebase was the first library on my project. So I kept using .xcodeproj file.