As of 4/27/18, this has been resolved and should now work natively. 

When using the pre-built Realm Swift framework in Xcode 9.3, you will receive a message like: 'Module compiled with Swift 4.0.2 cannot be imported in Swift 4.1:'

We are in the process of addressing this.  In the meantime, you have a few options: 

  • Manually build Realm locally after cloning our Cocoa repository.  Following steps like: 
$ git clone --recursive
$ cd realm-cocoa
$ sh ios-swift

            The resulting frameworks will be a folder like: build/ios/swift-4.1