I\'m having a look at the new Swift. I come from C, C++, Objective-C... I notice that in swift is not possible (?) to separate the declaration and the definition of function
In swift, there is no separation of declaration vs implementation. This works like most other modern languages like Python. If you want to get a quick picture of your class, you should use code folding. Simply fold all your methods and functions. And unfold a method of you want to modify / work on it.