How to declare Objective-C method with custom Swift class in it

Question

I want to declare an Objective-C method with a custom Swift class as one of it's arguments, like this:

+ (void)doCalculationsWithACustomSwiftObject:(CustomSwiftClass *)swiftObject andADictionanary:(NSDictionary *)ordinaryDictionary;

The aim is to call this method from Swift, pass an instance of the custom class "CustomSwiftClass.swift" so that the Objective-C code can access its properties. Is it possible, and if so, how do I declare the "CustomSwiftClass" to make the compiler accept it?

Answer 1

A couple of thoughts:

1. To make Swift class accessible to your Objective-C code, you have to import the system generated header. As the documentation says:

   When you import Swift code into Objective-C, you rely on an Xcode-generated header file to expose those files to Objective-C. This automatically generated file is an Objective-C header that declares the Swift interfaces in your target. It can be thought of as an umbrella header for your Swift code. The name of this header is your product module name followed by adding "-Swift.h". (You’ll learn more about the product module name later, in Naming Your Product Module.)

   For example, your Objective-C file would import this generated header:

   #import "MyApp-Swift.h"
   

   For more information, see Importing Swift into Objective-C section of the Using Swift with Cocoa and Objective-C: Mix and Match

2. If you're not seeing the xxx-Swift.h file, double check your target settings:

   

   (Note, I searched for "swift" in the settings to narrow down the results.)

   As you'll see, the following are all set:

   • "Install Objective-C Compatibility Header" is set to "Yes";

   • The "Objective-C Generated Interface Header Name" is set (and matches what I imported into my Objective-C code);

   • The "Objective-C Bridging Header" is also specified.

     Note, the Objective-C bridging header is ostensibly solely for the purpose of making the Objective-C classes available to the Swift code (and you're currently trying to accomplish the converse), but I notice that this affects what code is generated in the compatibility header, too. So make sure you have a bridging header, too.

3. Of course, make sure your Swift file is included in the list of compile sources:

   

4. And make sure the class is subclassed from NSObject:

   import UIKit
   
   class MyObject: NSObject {
       var text: String?
       var value: Int = 0
   }
   

5. Note, some Swift types are not available to Objective-C code. For example, Objective-C cannot not use some optional types (e.g. an optional type such as Int? will not work, whereas an optional class type of String? will). So if you are seeing the class, but not some of the properties, make sure they're Objective-C compatible.

   But I gather from your question that you're having more fundamental problems, that you're not finding the -Swift.h header at all. But once you solve that, this is a consideration for individual properties.