Call Swift function from Objective-C class

Question

I have an old Objective-C project and I want to call new Swift function and object, I have create the file "<ProjectName>-Bridging-Header.h" and "<ProjectName>-Swift.h"

was easy for me call the function from Swift to Objective-C but I have a problem for reverse.

So I have create a simple class "System.Swift"

import Foundation

@objc class System : NSObject {

    @objc func printSome() {
        println("Print line System");
    }
    
}

now I have try to follow the documentation here and inside the <...>-Swift.h file I have write this

@class System;

@interface System : NSObject

-(void)printSome;

@end

and I have import it inside my Objective-C Class. At this point inside my Objective C class (currently UIViewController) of my Objective-C code I have try to call "printSome" method:

- (void)viewDidLoad
{
    [super viewDidLoad];
    System * sis = [[System alloc] init];
    [sis printSome];
    //any additional setup after loading the view from its nib.
}

now I have the following Error:

Undefined symbols for architecture i386: "OBJC_CLASS$_System", referenced from: objc-class-ref in "ObjectiveC_Class_That_Call_Swift_Object".o ld: symbol(s) not found for architecture i386 clang: error: linker command failed with exit code 1 (use -v to see invocation)

You have a linker error. Is it: (1) Xcode uses your product module name—not your target name—when naming the Objective-C bridging header and the generated header for your Swift code, or (2) make sure to import the Objective-C headers for those types prior to importing the Swift generated header into the Objective-C .m file you want to access the Swift code from? Do you have: #import “ProductModuleName-Swift.h” in your Objective-C code? — petert
– petert, Commented Jun 6, 2014 at 9:25
Yes i have read the documentation and the name of "ProductModelName" is currect... There is a bug that inside the Build Setting the Product model was not set... i have even set it... — Eloreden
– Eloreden, Commented Jun 6, 2014 at 9:39
@petert can you explain better the second point? I wrote everithing i did... — Eloreden
– Eloreden, Commented Jun 6, 2014 at 10:11
Problem Solved, i have add a new .h file in my project call <ProductModelName>-Swift.h but this is not necessary because the compiler just create this object even if i can't see it. I have delete the new file that i have create and now all run perfectly. Tnx petert — Eloreden
– Eloreden, Commented Jun 6, 2014 at 10:46

Top-Master · Accepted Answer · 2021-06-28 17:49:19Z

68

It is strange but will work after we do:

Add @objc to your Swift-class ("MySwiftClass").
Add in Obj-C, i.e. the .m file:
```
#import "(ProjectName)-Swift.h"
```
Declare in header .h
```
@class MySwiftClass;
```

Compiler will generate the interface for @objc marked class in MyModuleName-Swift.h file.

Auto-Generated Obj-C Example:

SWIFT_CLASS("_TtC10Project17220PLHelper")
@interface PLHelper

+ (void)notifyForDownloading:(NSDictionary *)userInfo;
- (instancetype)init OBJC_DESIGNATED_INITIALIZER;
@end

edited Jun 28, 2021 at 17:49

Top-Master

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answered Nov 5, 2014 at 11:49

Svitlana

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6 Comments

nielsbot Over a year ago

You can also override the Obj-C name of your Swift class using @objc (MyClassName)

Hlung Over a year ago

For anyone who may do same dumb mistake as me. In step 2, make sure you use (ProjectName)-Swift.h, NOT (ClassName)-Swift.h !

Scofield Tran Over a year ago

thanks @Svitlana, unbelievable, it worked!!! But I have to retry many times these steps, including moving my added methods to other places in the class.

Mazen K Over a year ago

3) @class SwiftClassName; saved me

Rakshitha Muranga Rodrigo Over a year ago

if your target name has any spaces add "_" (underscores instead of spaces) when creating swift.h import eg: if your target name is Sample App then your import statement would be #import "Sample_App-Swift.h"

|

Patru · Accepted Answer · 2017-06-09 16:41:04Z

63

Problem Solved, I previously create and included a new .h file in my Objective-C class named <ProductModuleName>-Swift.h but, as i discovered later, this step is not necessary because the compiler creates the necessary file invisible.

Simply include <ProductModuleName>-Swift.h in your class and it should work.

edited Jun 9, 2017 at 16:41

Patru

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answered Jun 6, 2014 at 17:11

Eloreden

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6 Comments

Arnlee Vizcayno Over a year ago

how about functions with parameters?

idoodler Over a year ago

I am not able to access Swift functions with parameters and a return value, nor I am able to access Swift Functions without parameters and without a return value. I don't know why. My Swift Class is an NSObject, I imported the Foundation framework, the class and the functions have the @objc prefix. The -Swift.h has been automatically created. The thing that is making me headache is that I can call the Class itself but not any function inside it. Does anyone know why?

Paul Beusterien Over a year ago

good example at ericasadun.com/2014/08/21/…

SwiftArchitect Over a year ago

It is <productModuleName>-.Swift.h (not model).

EricRobertBrewer Over a year ago

If your Product name has any spaces in it, replace them with underscores, like: #import "My_Project-Swift.h".

|

Avijit Nagare · Accepted Answer · 2016-03-05 12:31:11Z

36

Assume We have ProjectName "MyFirstProjectOnSwift" and swift class name "mySwiftClass" and objectiveC class is "MyObjectiveCLass"

Following steps are:-

Add #import "MyFirstProjectOnSwift-Swift.h" in "MyObjectiveCLass.m"

Add @class mySwiftClass in MyObjectiveCLass.h;

Then in MyObjectiveCLass.m

mySwiftClass *myClass = [mySwiftClass new]; {Call Like This in any method wherever you want to call swift method.}

[myClass methodName];

edited Mar 5, 2016 at 12:31

Avijit Nagare

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answered Jan 19, 2016 at 10:13

Anubhav Giri

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2 Comments

Hari Narayanan Over a year ago

mySwiftClass *myClass = [mySwiftClass new] its not working for me>>>>>

Anubhav Giri Over a year ago

@HariNarayanan It should not be, do one think clear derived data and reopen your project.

Darius Miliauskas · Accepted Answer · 2015-12-21 23:48:37Z

13

Check the -Swift.h file which has the import on your .m file in objective-C:

#import <YourProjectName-Swift.h>

Click on that line, and left-click - Jump To Definition.

This file should be included automatically, not manually.

answered Dec 21, 2015 at 23:48

Darius Miliauskas

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1 Comment

Reece Over a year ago

My project name had a space in it; which looks like xcode replaced with an underscore for this file name. But if you type the < left angle bracket after the #import statement, and start typing your project name - you'll likely see the correct .h file listed in xcode's code completion popup.

Kqtr · Accepted Answer · 2019-12-04 12:52:35Z

7

Little additional tip for anyone stumbling upon this post and for hwhom the other answers do not work: you might also have to declare your Swift class "public".

Example:

@objc public class MySwiftClass: NSObject {

answered Dec 4, 2019 at 12:52

Kqtr

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Comments

Bryan P · Accepted Answer · 2017-10-11 09:30:05Z

2

If you're still not seeing your class even after importing <ProductModuleName>-Swift.h.

Make sure that your class is subclassing a native class (e.g UIViewController) or at least if it's just a utility class, make it subclass NSObject. Your class should now show.

answered Oct 11, 2017 at 9:30

Bryan P

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Comments

Javier Calatrava Llavería · Accepted Answer · 2020-04-23 12:25:22Z

The recomended way for executing Swift code from Objective-C on projects that are being migrated from Obj-C to Swift is using Bridge/Proxy pattern.

Implement the Bridge.

import Foundation

@objc class AnalyticsPropertyBridge: NSObject {

private var analytics: AnalyticsManager = AnalyticsManager()

@objc func refreshProperties() {

    self.analytics.set(AnalyticsProperty.clientType)
}

}

Include the objC caller module in the umbrella file (Bridging-Header):

#import "CallerModule.h"

Finally in the caller .m file, two issues:

3.a Import umbrella file:

#import "MyProject-Swift.h"

3.b Call the bridge.

[[AnalyticsPropertyBridge new] refreshProperties];

Benefits: Your swift code will not get dirty with @objc because code is being called from Objc. As time goes by, the ObjC will be reduced in your project and finally the bride will be removed.

Farhad Malekpour · Accepted Answer · 2021-02-19 23:19:57Z

0

A note about project name, if there are spaces in project name make sure you replace them with underscore, for example if project name is "My Project" you need to include:

#import <My_Project-Swift.h>

answered Feb 19, 2021 at 23:19

Farhad Malekpour

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Comments

Trident · Accepted Answer · 2020-09-04 16:55:19Z

-3

A good article out here if someone still having issues.

Setting up Swift and Objective-C Interoperability

This article discusses in-depth how to import Swift files into ObjC as well as Objc files to Swift.
It also addresses a problem generally faced when the Project name has space in it.
It also discusses about “Product Module Name” flag.

edited Sep 4, 2020 at 16:55

answered Sep 4, 2020 at 16:30

Trident

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1 Comment

Arghya Sadhu Over a year ago

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.

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