iOS developers build apps for the Apple iOS operating system, which powers iPhones and iPads. iOS developers will be skilled in Objective-C and Swift, which are the two main essential programming languages for iOS. An iOS developer will be responsible for developing and maintaining apps associated with iOS devices and will need to integrate the apps with back-end services. Thy should know other frameworks such as Core Data and Core Animation, know C-based libraries, be familiar with RESTful APIs and have a good understanding of code version tools, like Git.