Can I use an Objective-C class in my Swift framework library?

Question

I have created a Swift Framework that I use in multiple projects. There is an Objectivce-C class that I would like to use in that is difficult to port in straight Swift. Lets say that class is SFTest

@interface SFTest {
} 
+ (NString *)myMethod(NSString *data);
@end
@implementation SFTest
+ (NString *)myMethod(NSString *data) {
    // does some processing
    return processedData;
}
@end

Can I somehow use this in my Swift framework project, and if yes, how? My research on this mentions something called bridging headers but that they can't be used in Swift frameworks.

Answer 1

So this took a while but I finally got something to run on my device. Here is my setup. I created a Swift Framework called swiftlib. I added an Objective-C class called "MyClass". Basically it looks like this:

I then modified the "umbrella header" to import my new Objective-C class. The umbrella header is the name of your swift library project. So in my case, it was "swiftlib.h". This is what is inside my umbrella header file:

//
//  swiftlib.h
//  swiftlib
//

#import <UIKit/UIKit.h>
#import "MyClass.h"

//! Project version number for swiftlib.
FOUNDATION_EXPORT double swiftlibVersionNumber;

//! Project version string for swiftlib.
FOUNDATION_EXPORT const unsigned char swiftlibVersionString[];

// In this header, you should import all the public headers of your     framework using statements like #import <swiftlib/PublicHeader.h>

Make sure to set your header class to public or you will get a compile error. Basically whatever is included in the umbrella header is exposed to users of your swift framework so it needs to be public. Select MyClass.h and open the right details bar and select the dropdown here:

I then used this Swift framework in a single view application for testing and was able to use my Objective-C class in the AppDelegate.swift like so:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        // Override point for customization after application launch.
        let test = MyClass.myMethod()
        print("test = " + String(test))
        return true
    }

This compiled and ran on my device.

For those curious, this was the implementation code for the Objective-C MyClass:

#import "MyClass.h"
#import <CommonCrypto/CommonCrypto.h>

@implementation MyClass

+ (NSString *)myMethod {
    NSString *key = @"test";
    NSString *data = @"mytestdata";
    const char *ckey = [key cStringUsingEncoding:NSASCIIStringEncoding];
    const char *cdata = [data cStringUsingEncoding:NSASCIIStringEncoding];
    unsigned char chmac[CC_SHA256_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA256, ckey, strlen(ckey), cdata, strlen(cdata), chmac);
    NSData *hmac = [[NSData alloc] initWithBytes:chmac length:sizeof(chmac)];
    NSString *hash = [hmac base64Encoding];
    return hash;
}

@end