Mobile app Developer 📍 Tokyo, JP
environmentXcode: 9.0 GM (9A235)
Carthage: 0.25.0(tried on 2017/9/12)
In your existing xcode project, you might see this error if you convert swift version to 4.
I guess one of the most difficult part for newbie of Swift is how to handle optional type. This article, we’ll learn how to do that.