XCode 12: 'SessionDelegate' has different definitions in different modules

You can try SWIFT_INSTALL_OBJC_HEADER = NO, it works for me

The error is saying that you have multiple classes with the same name SessionDelegate in different modules. This error is related to Xcode 12.

For now, a quick solution is to install the module with CocoaPods (if you're using Carthage) and if needed, rename the SessionDelegate interface.

At this moment (Xcode 12.0 or Xcode 12.2b2), the only possible solution is to rename the Objective-C interface and avoid conflicts. This could be done by one of:

• Rename conflicting class entirely, update all places where it's used (e.g. replace SessionDelegate by KingfisherSessionDelegate)
• Add @objc(...) attribute to a Swift class, which will update the Obj-C interface in a generated ...-Swift.h file and avoid the names conflict.

//  SessionDelegate.swift
@objc(KFSessionDelegate)
class SessionDelegate: NSObject { ... }

//  Kingfisher-Swift.h
@interface KFSessionDelegate : NSObject
...
@end

This solution is already included in the Kingfisher 5.15.4 release and could be applied to any other libraries and your own frameworks.

Also, the thread on Apple forums: https://developer.apple.com/forums/thread/658012

If you guys need a temporary solution, here is how for Cocoapods users:

1. Clone the Kingfisher library to the same folder level with your project. You can get it from Github

2. Open Kingfisher.xcworkspace in XCode and rename SessionDelegate.swift file under Sources/Netowking to KingFisherSessionDelegate and change the class name as well accordingly.

3. Rename the usages of SessionDelegate to KingfisherSessionDelegate which is only available in Sources/Networking/ImageDownloader.swift as of Kingfisher version 5.15.0

4. Add local path in your Podfile

   pod 'Kingfisher', :path => '../Kingfisher'