Using Swift to Call Objective C Code

Swift is a new programming language that is purely compatible with objective C. This makes it possible to use objective C file code in Swift file. Apple claims the co-existence of Swift and Objective C in an application but, this does not relate to re-using old classes made  in Objective-C whilst building new classes in Swift. The reason being as Objective-C is a platform-independent language unlike  Swift is platform-dependent. Now, implementing non-platform-dependent code in Swift won’t be fruitful. henceforth, writing platform dependent code in Swift would be absolutely fine.

Step 1: Addition of Objective-C

Add a .m file in your class and give it a name  CustomObject.m.

Step 2: Addition of Bridging Header

While adding .m file it is quite likely you be prompted with something like this below:

image credit: stackoverflow

Simply click on YES !

In case you are not prompted or have unknowingly removed your bridging header then add a new .h file in your projecr and name it as  <#YourProjectName#>-Bridging-Header.h.

In some rare case while  working with Objective-C frameworks if you forget to add an Objective-C class explicitly and Xcode is unable to find the linker. Then, create your .h file named as mentioned above and ensure to link its path in your target’s project settings like below:

image credit: stackoverflow

It is a smart approach to link your project using $(SRCROOT) macro such that in case you want to move your project or work over it including others using remote repository it will work fine. $(SRCROOT) can be viewed as a directory that holds your xcodeproj file that look like below:

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

Step 3: Addition of Objective-C Header — .h

Add another .h file and name it as 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: Adding 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()

More ever there is no actual need to import explicitly as that is what the bridging header is for. Looking forward to respond to your queries and comments regarding code i have discussed for calling Objective C code using Swift.

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1. Right Approach to interact Objective-C Classes in CocoaScript