By David Mulder


2014-06-02 20:05:42 8 Comments

In the new Swift language from Apple, how does one call Objective-C code?

Apple mentioned that they could co-exist in one application, but does this mean that one could technically re-use old classes made in Objective-C whilst building new classes in Swift?

The Reasoning

Objective-C is a platform-independent language, whereas Swift is platform-dependent. Writing non-platform-dependent code (business logic libraries) in Swift would thus not be wise. However, writing platform-dependent code in it (interface related for example) would be perfectly fine. Not to say it would be a good idea, however it is definitely an interest.

17 comments

@yoAlex5 2019-08-04 09:23:17

Using Objective-C Classes in Swift

  1. Add Objective-C Header .h and Implementation .m
    Add a <FileName>.m and <FileName>.h files to your project

  2. Add Bridging Header
    When adding your .m file, click "Yes" on a promt Would you like to configure an Objective-C bridging header

  3. Add Class to Bridging-Header
    In YourProject-Bridging-Header.h add a line #import "<FileName>.h"

Using Swift Classes in Objective-C

  1. Add a <FileName>.swift file that extends NSObject to your project
  2. Import Swift Files to ObjC Class
    Add #import "<#YourProjectName#>-Swift.h" into your Objective-C file

Read more here

@Sazzad Hissain Khan 2019-05-21 13:48:29

Logans answer works fine except in latest Swift 5 it gives some compiler error. Here is the fix for people who are working on Swift 5.

Swift 5

import Foundation

class MySwiftObject : NSObject {

    var someProperty: AnyObject = "Some Initializer Val" as AnyObject

    override init() {}

    func someFunction(someArg:AnyObject) -> String {
        let returnVal = "You sent me \(someArg)"
        return returnVal
    }
}

@Sanjay Mali 2018-04-13 09:39:37

Two way Approach to use objective-c objective-c

1

  1. Create bridge-header.h file in Xcode Project
  2. import .h file in bridge-Header file
  3. Set path of bridge-Header in Build settings.
  4. Clean the Project

2

  1. Create objective-c files in project(it automatically set path in Build Settings for you )
  2. import .h file in bridge-Header file

Now good to go Thanks

@Johan Karlsson 2018-12-21 08:48:38

A very sparse answer.

@Logan 2014-06-03 00:12:17

Using Objective-C Classes in Swift

** If you have an existing class that you'd like to use, perform Step 2 and then skip to Step 5. (For some cases, I had to add an explicit #import <Foundation/Foundation.h to an older Objective-C File.) **

Step 1: Add Objective-C Implementation -- .m

Add a .m file to your class, and name it CustomObject.m.

Step 2: Add Bridging Header

When adding your .m file, you'll likely be hit with a prompt that looks like this:

Enter image description here

Click YES !

If you did not see the prompt, or accidentally deleted your bridging header, add a new .h file to your project and name it <#YourProjectName#>-Bridging-Header.h.

In some situations, particularly when working with Objective-C frameworks, you don't add an Objective-C class explicitly and Xcode can't find the linker. In this case, create your .h file named as mentioned above, then make sure you link its path in your target's project settings like so:

Enter image description here

Note

It's best practice to link your project using the $(SRCROOT) macro so that if you move your project, or work on it with others using a remote repository, it will still work. $(SRCROOT) can be thought of as the directory that contains your .xcodeproj file. It might look like this:

$(SRCROOT)/Folder/Folder/<#YourProjectName#>-Bridging-Header.h

Step 3: Add Objective-C Header -- .h

Add another .h file and name it CustomObject.h.

Step 4: Build your Objective-C Class

In CustomObject.h

#import <Foundation/Foundation.h>

@interface CustomObject : NSObject

@property (strong, nonatomic) id someProperty;

- (void) someMethod;

@end

In CustomObject.m

#import "CustomObject.h"

@implementation CustomObject 

- (void) someMethod {
    NSLog(@"SomeMethod Ran");
}

@end

Step 5: Add Class to Bridging-Header

In YourProject-Bridging-Header.h:

#import "CustomObject.h"

Step 6: Use your Object

In SomeSwiftFile.swift:

var instanceOfCustomObject: CustomObject = CustomObject()
instanceOfCustomObject.someProperty = "Hello World"
println(instanceOfCustomObject.someProperty)
instanceOfCustomObject.someMethod()

There is no need to import explicitly; that's what the bridging header is for.

Using Swift Classes in Objective-C

Step 1: Create New Swift Class

Add a .swift file to your project, and name it MySwiftObject.swift.

In MySwiftObject.swift:

import Foundation

class MySwiftObject : NSObject {

    var someProperty: AnyObject = "Some Initializer Val"

    init() {}

    func someFunction(someArg:AnyObject) -> String {
        var returnVal = "You sent me \(someArg)"
        return returnVal
    }   
}

Step 2: Import Swift Files to ObjC Class

In SomeRandomClass.m:

#import "<#YourProjectName#>-Swift.h"

The file:<#YourProjectName#>-Swift.h should already be created automatically in your project, even if you can not see it.

Step 3: Use your class

MySwiftObject * myOb = [MySwiftObject new];
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);
myOb.someProperty = @"Hello World";
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);

// original
NSString * retString = [myOb someFunction:@"Arg"];
// xcode10 expands the external arg here
NSString * retString = [myOb someFunctionWithSomeArg:@"Arg"];|

NSLog(@"RetString: %@", retString);

Note:

1. CodeCompletion wasn't behaving as accurately as I'd like it to. On my system, running a quick build with "cmd + r" seemed to help Swift find some of the Objective-C code and vice versa.

2. If you add a .swift file to an older project and get error: dyld: Library not loaded: @rpath/libswift_stdlib_core.dylib, try completely restarting Xcode.

3. While it was originally possible to use pure Swift classes in Objective-C by using the @objc prefix, after Swift 2.0, this is no longer possible. See edit history for original explanation. If this functionality is reenabled in future Swift versions, the answer will be updated accordingly.

@Tomáš Linhart 2014-06-03 11:19:06

It is important you need to annotate methods with @objc or Swift methods won't be visible from Objective-C.

@Logan 2014-06-03 13:41:53

@TomášLinhart -- I didn't find it necessary to do that, is there a specific use case you're referring to?

@Tomáš Linhart 2014-06-03 13:48:57

You are right. You only need to specify it if you don't use Cocoa objects. To be accessible and usable in Objective-C, a Swift class must be a descendant of an Objective-C class or it must be marked @objc.

@Markus Rautopuro 2014-06-03 16:17:45

Where is this <#YourProjectName#>-Swift.h? Is it generated at compile time?

@Logan 2014-06-03 16:22:05

@MarkusRautopuro - I don't know where it is in the directory, but it's generated automatically. The only way that I've been able to actually see it is when I had an error on it and I was able to click through the debugger to the file. Let me know if you find it.

@Markus Rautopuro 2014-06-03 16:23:26

By the way, where did you pull this information from (that <#YourProjectName#>-Swift.h exists)?

@Logan 2014-06-03 16:25:06

@Stuart M 2014-06-05 07:27:31

See also: WWDC 2014 Session 406: Integrating Swift with Objective-C

@Ravikumar S 2014-06-19 06:27:29

Guys I am new to iOS development. I am using Swift and trying to added XMLRPC libraries to my project. Xcode 6 not giving prompt for generating bridge-header file. Please help me on this

@Logan 2014-06-19 11:18:05

@ravivlb - Look at Step 2. Just add a '.h' w/ appropriate name.

@Ravikumar S 2014-06-19 11:33:43

Thank Logan. issue fixed by creating new project and added bridge header file.

@User 2014-10-07 03:19:30

What if the Objective C library has other Objective C dependencies?

@Logan 2014-10-07 13:11:23

@macdonjo - If those dependencies are included internally within the library, it should be fine as long as they're included in the project. If you need to access those libraries externally, I'm not positive, but I believe that as long as they are imported in the same header, you should be ok.

@user1021430 2014-11-20 21:29:24

If importing a Objective C framework into Swift, make sure to import all frameworks that the Obj C framework depends on into your project (in Build Phases -> Link Binary With Libraries), then add #import's for those to a prefix header file, which must be added to your project in build settings (in the Prefix Header field). This includes frameworks like UIKit and Foundation, even if those are already used from within Swift. This tripped me up for hours, and no one seems to have documented these steps.

@h4labs 2014-12-12 18:40:26

This was critical to add to my Objective C files that I wanted to import into Swift. I missed it and wasted a lot of time: #import <Foundation/Foundation.h>

@Andy 2015-08-07 14:44:37

@Logan why did you name it CustomClass.m and CustomClass.h? Couldn't this be named anything? What do I name these files if I want to create more than one?

@Logan 2015-08-07 14:54:02

@AndrewAnthonyGerst in objective-c it's convention to name the files after the name of the class, and there's rarely more than one class per file. So yes, you could name it anything, but I wouldn't recommend it. If you want more than one class, create a new .h and .m for each class.

@lee 2015-09-04 10:24:31

I my case Using Swift Classes in Objective-C. But get the error file not found when import #import "<#ProjectName#>-Swift.h". Please help me resolve this.

@Logan 2015-09-04 13:26:11

@lee - Can you go to your build settings and ensure that your Product Module Name is what you expect, the syntax is really #import "ProductModuleName-Swift.h, it just defaults to project name and most people don't change it.

@Sparkxxf 2015-11-21 03:54:29

In SomeSwiftFile.swift: I got this: Expected declaration on "instanceOfCustomObject.someProperty = "Hello World" Why?Thanks.

@AmJa 2016-04-27 21:39:36

Thanks @Logan this worked for me but the only thing I Noticed different is that with xcode 7.3 when you add .m or .h files there is no pop up coming for creating the bridging header you have to manually go to Build Settings and do it or may be something is wrong with my project settings :).

@Alper 2018-03-08 11:06:10

Why the hell does the -Swift.h file go into the .m file?

@Logan 2018-03-09 19:18:14

@Alper the system will generate a "bridging header" that exposes the accessible swift code to ObjC. This needs to be imported as any other file would be. For example, import OtherObject.h to import an ObjC class header. For Swift, we don't import classes individually, but rather need to import all accessible objects

@Alper 2018-03-09 20:25:54

But why not put it in the .h file?

@Logan 2018-03-09 20:46:33

@Alper that question is more about ObjC in general. If you import in the .h file, then all subsequent imports of that file will also import the other file. This can be useful if one object always needs another, but it can also lead to circular dependencies where A.h imports B.h imports C.h imports A.h. By putting it in the .m file, we keep it private to this class and subsequent imports don't also import that file. In Swift here, if we have Object.{h,m} and we imported in Object.h, then every time somebody imported Object.h in another file, they'd also import all Swift files.

@Oleksandr 2018-07-10 17:16:27

Works for 100%. One of the rarest cases. If you want to make this simpler you can: *create Obj.-C file *bridging-header will be generated. Describe all function in the generated file.

@djruss70 2019-01-13 13:12:55

In the section for Using Swift Classes in Objective-C, the Step 3 example shows calling a swift method with a parameter :someArg. In Xcode10, the given code gives an error “No visible @interface for 'MySwiftInterface' declares the selector 'someFunction:. To fix this error, the first parameter name should be incorporated into the method name, like this: NSString * retString = [myOb someFunctionWithSomeArg:@"Arg"];

@Clashsoft 2019-05-17 12:13:30

Image link is broken

@Honey 2019-08-11 12:17:52

If we you're interested about why header files are needed and how it's used during the linking phase, then make sure you read this Manual Swift: Understanding the Swift/Objective-C Build Pipeline @Logan You might want to add this link to the answer

@Tibin Thomas 2019-01-05 11:17:57

Apple has provided official guide in this doc: how-to-call-objective-c-code-from-swift

Here is the relevant part:

To import a set of Objective-C files into Swift code within the same app target, you rely on an Objective-C bridging header file to expose those files to Swift. Xcode offers to create this header when you add a Swift file to an existing Objective-C app, or an Objective-C file to an existing Swift app.

If you accept, Xcode creates the bridging header file along with the file you were creating, and names it by using your product module name followed by "-Bridging-Header.h". Alternatively, you can create a bridging header yourself by choosing File > New > File > [operating system] > Source > Header File

Edit the bridging header to expose your Objective-C code to your Swift code:

  1. In your Objective-C bridging header, import every Objective-C header you want to expose to Swift.
  2. In Build Settings, in Swift Compiler - Code Generation, make sure the Objective-C Bridging Header build setting has a path to the bridging header file. The path should be relative to your project, similar to the way your Info.plist path is specified in Build Settings. In most cases, you won't need to modify this setting.

Any public Objective-C headers listed in the bridging header are visible to Swift.

@ARGeo 2018-06-12 21:43:00

In the Swift 4.2.1 project in Xcode 10.1 you can easily add Objective-C file. Follow the steps below to bridge Objective-C file to Swift project.

Step_01: Create new Xcode project using Swift language:

File > New > Project > objc.

Step_02: In Swift project add new Objective-C file:

File > New > File... > macOS > Objective-C File.

Step_03: If you add a new Objective-C file into Swift project at very first time, Xcode asks you:

Would you like to configure an Objective-C bridging header?

enter image description here

Step_04: Select the option:

Create Bridging Header.

Step_05: A corresponding file will be generated with a name:

Objc-Bridging-Header.h.

enter image description here

Step_06: Now, you need setup Bridge file path in bridge header. In Project Navigator click on project with name objc and then choose:

Build Settings > Objective-C Bridging Header > Objc-Bridging-Header.h.

Step_07: Drag-and-drop your Objc-Bridging-Header.h into that box to generate a file path.

enter image description here

Step_08: Open your Objc-Bridging-Header.h file and import the Objective-C file which you want to use in your Swift file.

#import "SpecialObjcFile.m"

Here's a content of SpecialObjcFile.m:

#import <Foundation/Foundation.h>

@interface Person: NSObject {
@public
    bool busy;
}
@property
    bool busy;
@end

Step_09: Now in your Swift file, you can use an Objective-C class:

override func viewDidLoad() {
    super.viewDidLoad()
    let myObjcContent = Person()
    print(myObjcContent.busy)
}

enter image description here enter image description here

@Shubham Mishra 2018-12-07 17:13:21

xcode 9.4 doesn't support swift 4.2

@Kampai 2015-09-16 07:00:57

One more thing I would like to add here:

I am very thankful for @Logan's answer. It helps a lot to create a bridge file and setups.

But after doing all these steps I'm still not getting an Objective-C class in Swift.

I used the cocoapods library and integrated it into my project. Which is pod "pop".

So if you are using Objective-C pods in Swift then there may be a chance that you can not able to get or import the classes into Swift.

The simple thing you have to do is:

  1. Go to <YOUR-PROJECT>-Bridging-Header file and
  2. Replace the statement #import <ObjC_Framework> to @import ObjC_Framework

For example: (Pop library)

Replace

#import <pop/POP.h>

with

@import pop;

Use clang import when #import is not working.

@Honey 2016-12-02 03:44:19

Use clang import when #import is not working. what? Didn't just say we should use @import ?!

@CrazyPro007 2018-05-19 16:27:52

enter image description hereI have added the project on github that include small sample to call objective c code from swift.

Call ObjectiveC class from swift

@CrazyPro007 2018-05-19 16:30:13

NOTE:- When you create a Objc class in swift project than xcode asks for bridging the class automatically. No worries :)

@Nish 2017-06-29 06:38:20

  1. Create a .h file from NewFile -> Source -> header file
  2. Then save the name of file Your_Target_Name-Bridging-Header.h People here gets common mistake by taking their project name but it should be the Project's Target's name if in case both are different, generally they are same.
  3. Then in build settings search for Objective-C Bridging Header flag and put the address of your newly created bridging file, you can do it right click on the file -> show in finder -> drag the file in the text area then the address will be populated.
  4. Using #import Your_Objective-C_file.h
  5. In the swift file you can access the ObjC file but in swift language only.

@david72 2016-03-20 17:53:31

Just a note for whoever is trying to add an Objective-C library to Swift: You should add -ObjC in Build Settings -> Linking -> Other Linker Flags.

@Johan Karlsson 2018-12-21 08:48:00

Why? Please add information on what this flag does and why it should be added.

@Avijit Nagare 2015-11-25 08:29:40

After you created a Bridging header, go to Build Setting => Search for "Objective-C Bridging Header".

Just below you will find the ""Objective-C Generated Interface Header Name" file.

Import that file in your view controller.

Example: In my case: "Dauble-Swift.h"

eEter image description here

@Yogesh shelke 2015-09-10 12:16:36

Click on the New file menu, and chose file select language Objective. At that time it automatically generates a "Objective-C Bridging Header" file that is used to define some class name.

"Objective-C Bridging Header" under "Swift Compiler - Code Generation".

@derrrick 2015-02-12 19:34:25

Here are step-by-step instructions for using Objective-C code (in this case, a framework provided by a third-party) in a Swift project:

  1. Add any Objective-C file to your Swift project by choosing File -> New -> New File -> Objective-C File. Upon saving, Xcode will ask if you want to add a bridging header. Choose 'Yes'. Gif: adding empty file to project and generating bridging header http://www.derrrick.com/stackoverflow/1-empty-file.gif

In simple steps:

  1. A prompt appears, and then click on OK... If it does not appear, then we create it manually like in the following... Create one header file from iOS source and give the name ProjectName-Bridging-Header (example: Test-Bridging-Header), and then go to build setting in the Swift compiler code -> Objective-C bridge add Objective-C bridge name ..(Test/Test-Bridging-Header.h). Yeah, that's complete.

  2. Optionally, delete the Objective-C file you added (named "anything" in the GIF image above). You don't need it any more.

  3. Open the bridging header file -- the filename is of the form [YourProject]-Bridging-Header.h. It includes an Xcode-provided comment. Add a line of code for the Objective-C file you want to include, such as a third-party framework. For example, to add Mixpanel to your project, you will need to add the following line of code to the bridging header file:

    #import "Mixpanel.h"
  4. Now in any Swift file you can use existing Objective-C code, in the Swift syntax (in the case of this example, and you can call Mixpanel SDK methods, etc.). You need to familiarize yourself with how Xcode translates Objective-C to Swift. Apple's guide is a quick read. Or see this answer for an incomplete summary.

Example for Mixpanel:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    Mixpanel.sharedInstanceWithToken("your-token")
    return true
}

That's it!

Note: If you remove the bridging header file from your project, be sure to go into Build Settings and remove the value for "Objective-C Bridging Header" under "Swift Compiler - Code Generation".

@Gian Luigi Romita 2014-06-13 10:10:00

I wrote a simple Xcode 6 project that shows how to mix C++, Objective-C and Swift code:

https://github.com/romitagl/shared/tree/master/C-ObjC-Swift/Performance_Console

In particular, the example calls an Objective-C and a C++ function from the Swift.

The key is to create a shared header, Project-Bridging-Header.h, and put the Objective-C headers there.

Please download the project as a complete example.

@Jake Lin 2014-06-04 02:11:55

You can read the nice post Swift & Cocoapods. Basically, we need to create a bridging header file and put all Objective-C headers there. And then we need to reference it from our build settings. After that, we can use the Objective-C code.

let manager = AFHTTPRequestOperationManager()
manager.GET(
  "http://example.com/resources.json",
  parameters: nil,
  success: { (operation: AFHTTPRequestOperation!,
              responseObject: AnyObject!) in
      println("JSON: " + responseObject.description)
  },
  failure: { (operation: AFHTTPRequestOperation!,
              error: NSError!) in
      println("Error: " + error.localizedDescription)
  })

Also have a look at Apple's document Using Swift with Cocoa and Objective-C as well.

@rickster 2014-06-02 20:43:51

See Apple's guide to Using Swift with Cocoa and Objective-C. This guide covers how to use Objective-C and C code from Swift and vice versa and has recommendations for how to convert a project or mix and match Objective-C/C and Swift parts in an existing project.

The compiler automatically generates Swift syntax for calling C functions and Objective-C methods. As seen in the documentation, this Objective-C:

UITableView *myTableView = [[UITableView alloc] initWithFrame:CGRectZero style:UITableViewStyleGrouped];

turns into this Swift code:

let myTableView: UITableView = UITableView(frame: CGRectZero, style: .Grouped)

Xcode also does this translation on the fly — you can use Open Quickly while editing a Swift file and type an Objective-C class name, and it'll take you to a Swift-ified version of the class header. (You can also get this by cmd-clicking on an API symbol in a Swift file.) And all the API reference documentation in the iOS 8 and OS X v10.10 (Yosemite) developer libraries is visible in both Objective-C and Swift forms (e.g. UIView).

@skywinder 2014-06-04 11:55:07

The direct link to Apple documentation how to integrate Swift in existing project: developer.apple.com/library/prerelease/ios/documentation/Swi‌​ft/…

@Honey 2019-08-11 12:16:06

If we you're interested about why header files are needed and how it's used during the linking phase, then make sure you read this Manual Swift: Understanding the Swift/Objective-C Build Pipeline

@Gergo Erdosi 2014-06-02 20:43:55

Quote from the documentation:

Any Objective-C framework (or C library) that’s accessible as a module can be imported directly into Swift. This includes all of the Objective-C system frameworks—such as Foundation, UIKit, and SpriteKit—as well as common C libraries supplied with the system. For example, to import Foundation, simply add this import statement to the top of the Swift file you’re working in:

import Foundation

This import makes all of the Foundation APIs—including NSDate, NSURL, NSMutableData, and all of their methods, properties, and categories—directly available in Swift.

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