Can Objective-C code call Swift class extensions?

Question

I searched some posts, I think I cannot write an extension under Swift, and call it from Objective-C code, right?

@objc like attributes only support methods, class, protocols ?

Answer 1

You can write a Swift extension and use it in Objective-C code. Tested with Xcode 6.1.1.

All you need to do is:

• create your extension in Swift (@objc annotation needed since Swift 4.0.3)

• #import "ProjectTarget-Swift.h" in your Objective-C class (where "ProjectTarget" represents the XCode target the Swift extension is associated with)

• call the methods from the Swift extension

Answer 2

I found out that in Swift 4.0 I had to add @objc in front of my extension keyword in order for the Swift extension methods to become visible by an instance of the Objc class I was extending.

In short:

File configuration setup:

CustomClass.h CustomClass.m CustomClassExtension.swift 

In CustomClassExtension:

@objc extension CustomClass {     func method1()      {         ...     } } 

In my AppDelegate.m:

self.customClass = [[CustomClass alloc] init]; [self.customClass method1];