How do I call Objective-C code from Swift

Question

In Swift  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

User · Answer

You can read the nice post Swift  amp  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

User · Answer

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     Step 04  Select the option    Create Bridging Header   Step 05  A corresponding file will be generated with a name     Objc-Bridging-Header h     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     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  lt Foundation Foundation h gt    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

User · Answer

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  quot pop quot   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   Go to  lt YOUR-PROJECT gt -Bridging-Header file and Replace the statement  import  lt ObjC Framework gt  to  import ObjC Framework  For example   Pop library  Replace  import  lt pop POP h gt   with  import pop   Use clang import when  import is not working

User · Answer

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 nbsp 8 and OS nbsp X v10 10  Yosemite  developer libraries is visible in both Objective-C and Swift forms  e g  UIView

User · Answer

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

User · Answer

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

User · Answer

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    quot Some Initializer Val quot  as AnyObject      override init           func someFunction someArg AnyObject  - gt  String           let returnVal    quot You sent me   someArg  quot          return returnVal

User · Answer

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

User · Answer

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

User · Answer

Two way Approach to use objective-c  objective-c  1   Create bridge-header h file in Xcode Project import  h file in bridge-Header file Set path of bridge-Header in Build settings   Clean the Project    2   Create objective-c files in project it automatically set path in Build Settings for you   import  h file in bridge-Header file   Now good to go Thanks

User · Answer

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    In your Objective-C bridging header  import every Objective-C header you want to expose to Swift  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

User · Answer

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

User · Answer

Create a  h file from NewFile -  Source -  header file 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  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  Using  import Your Objective-C file h In the swift file you can access the ObjC file but in swift language only

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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    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     source  derrrick com      In simple steps    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  Optionally  delete the Objective-C file you added  named  anything  in the GIF image above   You don t need it any more  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  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    - gt  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

User · Answer

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  lt 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     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  lt  YourProjectName  gt -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     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  lt  YourProjectName  gt -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  lt Foundation Foundation h gt    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   instanceOfCustomObject someProperty    Hello World  print 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   objc MySwiftObject  class MySwiftObject   NSObject         objc     var someProperty  AnyObject    Some Initializer Val  as NSString      init            objc     func someFunction someArg  Any  - gt  NSString           return  You sent me   someArg             Step 2  Import Swift Files to ObjC Class  In SomeRandomClass m    import   lt  YourProjectName  gt -Swift h    The file  lt  YourProjectName  gt -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    NSString   retString    myOb someFunctionWithSomeArg   Arg     NSLog   RetString       retString     Notes    If Code Completion isn t behaving as you expect  try running a quick build with   R to help Xcode find some of the Objective-C code from a Swift context and vice versa   If you add a  swift file to an older project and get the error dyld  Library not loaded   rpath libswift stdlib core dylib  try completely restarting Xcode  While it was originally possible to use pure Swift classes  Not descendents of NSObject  which are visible to Objective-C by using the  objc prefix  this is no longer possible  Now  to be visible in Objective-C  the Swift object must either be a class conforming to NSObjectProtocol  easiest way to do this is to inherit from NSObject   or to be an enum marked  objc with a raw value of some integer type like Int  You may view the edit history for an example of Swift 1 x code using  objc without these restrictions

User · Answer

Swift consumer  Objective-C producer  Add a new header  h and Implementation  m files - Cocoa class file Objective-C  For example MyFileName   configure bridging header When you see Would you like to configure an Objective-C bridging header click - Yes     lt target name gt -Bridging-Header h will be generated automatically Build Settings - gt  Objective-C Bridging Header   Add Class to Bridging-Header In  lt target name gt -Bridging-Header h add a line  import  quot  lt MyFileName gt  h quot   After that you are able to use MyFileName from Objective-C in Swift P S  If you should add an existing Objective-C file into Swift project add Bridging-Header h beforehand and import it Objective-C consumer  Swift producer  Add a  lt MyFileName gt  swift and extends NSObject  Import Swift Files to ObjC Class Add  import  quot  lt target name gt -Swift h quot  into your Objective-C file  Expose public Swift code by  objc   objc and  objcMembers    After that you are able to use Swift in Objective-C Conclusion Using this approach you can use both Swift and Objective-C codebase in the same project

User · Answer

Making any Swift class subclass of NSObject makes sense also I prefer for using any Swift class to be seen in Objective-C classes like   objc MySwiftClass   objcMembers class MySwiftClass

[objective-c] How do I call Objective-C code from Swift?

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