SimpleFramework

Overview

The purpose of this project is to demonstrate (and remember) how to create a Swift framework for iOS that in turn uses Objective-C code. Then, this framework is used by two different iOS apps -- one Swift and one Objective-C.

Creating the Framework

1. Create a new Xcode project.
2. Create a new Cocoa Touch framework target using Swift.
3. Create a new Objective C Cocoa Touch class named SFClass as a subclass of NSObject.
4. Select SFClass.h and make sure its Target Membership is SimpleFramework and "Public". Turns out this is critical.
5. Add the following code to SFClass.h:

-(void) printMessage:(NSString *) message;

1. Add the following code to SFClass.m:

-(void) printMessage:(NSString *) message {
 NSLog(@"The message is %@", message);
}

1. Create a new Swift class named SimpleClass as a subclass of NSObject and add the following code to SimpleClass.swift. Note the usage of public in front of the class, the initializer, and the printMessage method. This makes the class and methods available to those who consume the framework.

public class SimpleClass: NSObject {
 
 var message: String
 var object: SFClass = SFClass()
 
 public init(_ newMessage: String) {
   self.message = newMessage
 }
 
 public func printMessage() {
   object.printMessage(self.message)
 }
}

1. When you created the framework target, Xcode automatically created SimpleFramework.h for you. Add the following to that file:

#import "SFClass.h"

Consuming the Framework from a Swift app

1. Create a new single-view iOS app target in the project and name it SwiftApp and use Swift.
2. Select the new target and go to the General settings. Under Embedded Binaries, click the + and add SimpleFramework.framework.
3. In the ViewController.swift file that was created, add the following line at the top:

import SimpleFramework

and the following method should replace the existing viewDidLoad:

 override func viewDidLoad() {
   super.viewDidLoad()
   let sc = SimpleClass("Hello Swift framework from Swift!!!")
   sc.printMessage()
 }

Consuming the Framework from an Objective-C app

1. Create a new single-view iOS app target in the project and name it ObjCApp and use Objective C.
2. Select the new target and go to the General settings. Under Embedded Binaries, click the + and add SimpleFramework.framework.
3. Under the Build Settings for the target, find the setting for Embedded Content Contains Swift Code and set it to Yes.
4. In the ViewController.m file that was created, add the following line at the top:

@import SimpleFramework;

and the following method should replace the existing viewDidLoad:

- (void)viewDidLoad {
 [super viewDidLoad];
 SimpleClass *sc = [[SimpleClass alloc] init:@"Hello Swift framework from Objective C!!!"];
 [sc printMessage];
}