iOS - Facebook Login Error - Unknown Error building URL (com.facebook.sdk.core error 3)

Question

I am using Facebook login for my iOS app being developed for iOS 8 and onwards. (Latest Facebook SDK is being used)

I have followed all the essential steps described by

Answer 1

If you upgraded the Facebook iOS SDK to version 4.39.0, there is a bug that causes this error. Downgrade to 4.38.1 will help you solve this problem. Be sure to downgrade both FBSDKCoreKit and FBSDKLoginKit.

pod 'FBSDKCoreKit', '~> 4.38.0'
pod 'FBSDKLoginKit', '~> 4.38.0'

Be sure to clean the build folder and re-build the SDK.

update: This bug has been fixed in 4.39.1 SDK release. https://developers.facebook.com/docs/ios/change-log-4x/