This course is designed to teach students how to understand and identify the differences between the Objective-C and Swift programming languages, and especially, how to rewrite from the former to the latter. Understanding communications between the two languages—called "interoperability"—is becoming more and more important for developers, particularly as we prepare for the arrival of Swift 3.0. In the course, students will write classes and add functionality to classes by writing and calling methods. After learning some basic Objective-C syntax, students will examine and break down an app written in Objective-C and rewrite it in Swift. The course will conclude with a review of and practice with the most common challenges for interoperability between Objective-C and Swift.