are extensions bad for performance in swift?

Question

Swift offers the ability to write extensions. I do that a lot to make my code easier to read. Not sure if they are harmless. I am wondering, would it be better to just omit

Answer 1

You don't need to worry about that. Compiler while compiling, treat these extensions as much as like a just another function call. Because extension is not a dynamic behavior but a static one. When you use performSelector it costs more performance than a normal instance method or extension as it is a dynamic behavior.

Answer 2

Apple encourages the use of extensions. You can read more about them on the Swift documentation here.