The object model of RubyMotion is based on Objective-C, the underlying language runtime of the iOS and OS X SDK. Objective-C is an object-oriented flavor of C that has been, like Ruby, heavily influenced by the Smalltalk language.
Sharing a common ancestor, the object models of Ruby and Objective-C are conceptually similar. For instance, both languages have the notion of open classes, single inheritance and single dynamic message dispatch.
In RubyMotion, Ruby classes, methods and objects are Objective-C classes, methods and objects respectively. The converse is also true. Objective-C classes, methods and objects are available in Ruby as if they were native.RubyMotion implements the Ruby object model by using the Objective-C runtime, the library that powers the Objective-C language and indirectly, the iOS SDK APIs.
By sharing the same object model infrastructure, Objective-C and RubyMotion APIs can be interchangeable at no additional performance expense.