how to use Notification.Name extension from swift 3 to Objective-C

My extension in swift file

extension Notification.Name {
    static let purchaseDidFinish = Notification.Name("purchaseDidFinish")
}

@objc extension NSNotification {
    public static let purchaseDidFinish = Notification.Name.purchaseDidFinish
}

---

// OBJECTIVE-C

#import YourProjectName-Swift.h

[NSNotificationCenter.defaultCenter addObserver:self selector:@selector(purchaseDidFinish) name:NSNotification.purchaseDidFinish object:nil];

---

// SWIFT
NotificationCenter.default.addObserver(self, selector: #selector(purchaseDidFinish), name: .purchaseDidFinish, object: nil)

---

@objc func purchaseDidFinish(notification: Notification) {
    print("purchaseDidFinish")
}

@leanne's answer was super helpful

Notification.Name doesn't exist in Objective-C. And the Objective-C type NotificationName is really just an NSString. To use Swift stuff in Objective-C, the class must be available in both, and can't be a Swift struct (like Notification or String, say).

To do what you want, then, you need to have two extensions:

• one for the Swift Notification.Name, as you have; and,
• one for an Objective-C object (NSString, say, or perhaps NSNotification if you prefer).

1) Add an Objective-C-compatible object extension to your Swift file:

public extension NSNotification {
    public static let blahblahblah: NSString = "blahblahblah"
}

Note: in Swift 4, properties must be computed for Objective-C compatibility. That would look like:

@objc public extension NSNotification {
    public static var blahblahblah: NSString {
        return "blahblahblah"
    }
}

Note the var in the computed property: computed properties can't be immutable, so can't use let.

2) In the Objective-C file, import Xcode's generated Swift header file (below any other imports):

#import "YourProjectName-Swift.h"

Note: replace YourProjectName with the actual name of your project. So, if your project is named "CoolGameApp", the Swift header would be "CoolGameApp-Swift.h". If your project name has spaces, like "Cool Game App", replace them with dashes: "Cool-Game-App-Swift.h"

3) Rebuild the project.

Now, you should be able to access the extension in Objective-C:

[[NSNotificationCenter defaultCenter] postNotificationName:NSNotification.blahblahblah object:self];

In addition to the answers here, I had to add @objc to my NSNotification extension before my Obj-C code could see it (Swift 4).