We are trying to reference Swift methods inside an Objective-C implementation.
Swift class:
import Foundation
#objc class MySwiftClass: NSObject {
override init() {
super.init()
}
func sayHello() -> Void {
print("hello");
}
func addX(x:Int, andY y:Int) -> Int {
return x+y
}
}
Objective-C implementation (Objective-c.m):
#import "ProductModuleName-Swift.h"
MySwiftClass* getData = [[MySwiftClass alloc]init];
[getData sayHello] //works
[getData addX:5 addY:5] //No visible #interface for 'MySwiftClass' declares selector 'addX:addY'
The last line of code gives the following error:
No visible #interface for 'MySwiftClass' declares selector 'addX:addY'
If you command-click on "ProductModuleName-Swift.h" in the Xcode
source file editor then you can see how the Swift methods are mapped to Objective-C.
In your case that would be
#interface MySwiftClass : NSObject
- (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
- (void)sayHello;
- (NSInteger)addXWithX:(NSInteger)x andY:(NSInteger)y;
#end
which is called as
MySwiftClass* getData = [[MySwiftClass alloc]init];
[getData sayHello];
NSInteger result = [getData addXWithX:5 andY:5];
A better Swift 3 method name might be
func add(x: Int, y:Int) -> Int
because x is already the argument (external) name of the first
parameter. You can also add an #objc() attribute to the Swift definition
to control the Objective-C name. For example, with
#objc(addX:andY:)
func add(x: Int, y: Int) -> Int {
return x+y
}
it would be called from Objective-C as
NSInteger result = [getData addX:5 andY:5];
As #ekscrypto pointed out, in Swift 4 and later you need to annotate individual functions with #objc. Prior to that, a single, class-level #objc was enough.
Of course in Objective-C class you must add import of NAME_PROJECT-swift.h.
If your project name is Sample then you must add:
#import Sample-swift.h
And then:
Swift 4 or Less
#objc class MySwiftClass: NSObject {
func sayHello(){
//function
}
func addX(){
//function
}
}
Swift 4 or Greater
#objc class MySwiftClass: NSObject {
#objc func sayHello(){
//function
}
#objc func addX(){
//function
}
}
In my case I had forgotten to add:
#import "MyProject-Swift.h"
Into the obj c file.
Related
I'm attempting to slowly migrate an Objective C app over to Swift and have started to create new classes -
public class MapsAPI : NSObject {
let delegate: MapsAPIResponseDelegate
public init(managerWithDelegate delegate: MapsAPIResponseDelegate) {
self.delegate = delegate
}
}
Now in my Objective C .m file I've declared #import MyTarget-Swift.h and in my .h I've added #class MapsAPI which all seems fine however I'm not sure what the Objective C initialisation code should look like. I've tried -
MapsAPI *api = [[MapsAPI alloc] initWithManagerWithDelegate: self];
But that errors with -
No visible #interface for 'MapsAPI' declares the selector
'initWithManagerWithDelegate:'
I've tried looking at the definition of my MyTarget-Swift.h but all that shows is -
SWIFT_CLASS("_TtC4What7MapsAPI")
#interface MapsAPI : NSObject
- (nonnull instancetype)init SWIFT_UNAVAILABLE;
#end
Is there something I'm doing wrong here?
You may choose to add #objcMembers to your class declaration:
public class #objcMembers MapsAPI : NSObject {
let delegate: MapsAPIResponseDelegate
public init(managerWithDelegate delegate: MapsAPIResponseDelegate) {
self.delegate = delegate
}
}
Alternatively (or additionally... who am I to judge) you can mark your initializer as being exposed to Objective-C
public class MapsAPI : NSObject {
let delegate: MapsAPIResponseDelegate
#objc public init(managerWithDelegate delegate: MapsAPIResponseDelegate) {
self.delegate = delegate
}
}
And if you want to, you can also explicitly define the Objective-C selector used:
public class MapsAPI : NSObject {
let delegate: MapsAPIResponseDelegate
#objc(initManagerWithDelegate:)
public init(managerWithDelegate delegate: MapsAPIResponseDelegate) {
self.delegate = delegate
}
}
I have created on Class in Swift and that class and its protocol I am using in Obj-C enabled project but I am getting below error while compiling my project.
cannot find protocol declaration for 'SpeechRecognizerDelegate'; did
you mean 'SFSpeechRecognizerDelegate'?
Can anyone guide me on this how can I use Swift class protocol in my Obj-C class.
Here is my Swift code:
protocol SpeechRecognizerDelegate : class {
func speechRecognitionFinished(_ transcription:String)
func speechRecognitionError(_ error:Error)
}
class SpeechRecognizer: NSObject, SFSpeechRecognizerDelegate {
open weak var delegate: SpeechRecognizerDelegate?
}
Protocol use in Obj-C:
#import "ARBot-Swift.h"
#interface ChatScreenViewController : JSQMessagesViewController <SpeechRecognizerDelegate>
Let me know if required more info.
Thanks in Advance.
in Swift:
#objc public protocol YOURSwiftDelegate {
func viewReceiptPhoto()
func amountPicked(selected: Int)
}
class YourClass: NSObject {
weak var delegat: YOURSwiftDelegate?
}
in Objective-C headerFile.h
#protocol YOURSwiftDelegate;
#interface YOURController : UIViewController < YOURSwiftDelegate >
in Objective-C Implementation.m
SwiftObject * swiftObject = [SwiftObject alloc] init];
swiftObject.delegate = self
Define your Swift protocol like this inside your Swift file.
#objc protocol SpeechRecognizerDelegate: class{
func speechRecognitionFinished(_ transcription:String)
func speechRecognitionError(_ error:Error)
}
Create a Swift Module inside your project setting then use it. You can find here complete blog for the mix language coding.
Then use Protocol inside Objective C class,
We required to add protocol inside Objective C file -
#import "ARBot-Swift.h"
#interface ChatScreenViewController : JSQMessagesViewController <SpeechRecognizerDelegate>
Then you need to conform to the protocol methods -
- (void)viewDidLoad {
[super viewDidLoad];
SpeechRecognizer * speechRecognizer = [[SpeechRecognizer alloc] init];
speechRecognizer.delegate = self;
}
#pragma mark - Delegate Methods
-(void)speechRecognitionFinished:(NSString *) transcription{
//Do something here
}
-(void)speechRecognitionError:(NSError *) error{
//Do something here
}
I had a similar issue after following (import header + Objc annotation on protocol). I got the warning when using Swift code from Objective C headers. Solved by only importing into the implementation .m files.
Add #objc attribute to your protocol:
#objc protocol SpeechRecognizerDelegate : class {
//...
}
Include Swift Classes in Objective-C Headers Using Forward Declarations
//MySwiftClass.swift
#objc protocol MySwiftProtocol {}
#objcMembers class MySwiftClass {}
// MyObjcClass.h
#class MySwiftClass;
#protocol MySwiftProtocol;
#interface MyObjcClass : NSObject
- (MySwiftClass *)returnSwiftClassInstance;
- (id <MySwiftProtocol>)returnInstanceAdoptingSwiftProtocol;
// ...
#end
My intention is to create a generic class in Swift which conforms to an Objective-C protocol:
The class is:
class BaseViewFactoryImpl<T> : NSObject, BaseView {
func getNativeInstance() -> AnyObject {
return String("fsd")
}
}
The protocol BaseView is:
#protocol BaseView < NSObject >
- (id)getNativeInstance;
#end
The compiler tells me:
Type 'BaseViewFactoryImpl<T>' does not conform to protocol 'BaseView'
If I delete <T> then there is no error.
What is wrong here? How can I get the correct generic class implementation?
//BaseViewFactory.swift
class BaseViewFactoryImpl<T> : NSObject, BaseView {
func getNativeInstance() -> AnyObject {
return String("fsd")
}
//BaseViewProtocol.h
#protocol BaseView <NSObject>
- (id)getNativeInstance;
#end
//BridgingHeader.h
#import "BaseClassProtocol.h"
Your code should work. Have you created the bridging header to import the obj-C protocol file?
Starting with Swift 3, you need to use Any, not AnyObject, to represent generic id values coming from Objective-C.
This builds with no errors:
class BaseViewFactoryImpl<T> : NSObject, BaseView {
func getNativeInstance() -> Any {
return "fsd"
}
}
If you create a new generic view model, when you try to create any subclass of the generic view model, you need to declare the subclass as a generic class as well. It's kind of annoy.
For a better way, you can use typealias to declare the instance's type instead of using generic:
protocol BaseView {
typealias T
func getNativeInstance() -> T!
}
class StringViewModel : BaseView {
typealias T = String
func getNativeInstance() -> String! {
return T()
}
}
I'm now learning a function which is written in Objective-C. But I don't know Objective-C language. When I'm converting the code to Swift, I got stuck at the delegate functions.
The code in .h file is:
#import <UIKit/UIKit.h>
#protocol SCPopViewDelegate <NSObject>
#optional
- (void)viewHeight:(CGFloat)height;
- (void)itemPressedWithIndex:(NSInteger)index;
#end
#interface SCPopView : UIView
#property (nonatomic, weak) id <SCPopViewDelegate>delegate;
#property (nonatomic, strong) NSArray *itemNames;
#end
and I'm trying to convert the code as:
protocol popViewDelegate: class {
func itemPressedWithIndex(index: Int)
func viewHeight(height: CGFloat)
}
but for the three last sentences, i don’t know how to deal with them, especially the one with id and delegate.
Can I get any help, please? I will do more effort to learn Swift. Thank you very much!
Swift 4.2
Converted Code for Swift 4.2
protocol SCPopViewDelegate: class {
func viewHeight(_ height: CGFloat)
func itemPressed(with index: Int)
}
extension SCPopViewDelegate {
func viewHeight(_ height: CGFloat) {}
func itemPressed(with index: Int) {}
}
class SCPopView: UIView {
weak var delegate: SCPopViewDelegate?
var itemNames: [Any] = []
}
This code is based on code converted by an online code conversion tool, the link to the original generated code.
The definition of the protocol ends with the first #end statement.
The #interface after that is the definition of an Objective-C class, SCPopView.
You don't need to care about the latter part if you're just trying to define the protocol in Swift.
FYI:
#interface someClass: NSObject
is equivalent to
class someClass: NSObject
In Swift.
import UIKit
#objc protocol SCPopViewDelegate{
optional func viewHeight(height: Float)
optional func itemPressedWithIndex(index : Int)
}
class DGViewController: UIViewController {
var delegate:SCPopViewDelegate! = nil
override func viewDidLoad() {
super.viewDidLoad()
delegate?.viewHeight?(Float(self.view.frame.size.height))
}
And in the class that implements the delegate
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
var vc = DGViewController()
vc.delegate = self
vc.view.frame = self.view.frame;
vc.view.backgroundColor = (UIColor.redColor())
self.presentViewController(vc, animated: true) { () -> Void in}
}
func viewHeight(height: Float) {
println(height)
}
I'm having some trouble accessing a Swift Singleton from Objective-C.
#objc class SingletonTest: NSObject {
// swiftSharedInstance is not accessible from ObjC
class var swiftSharedInstance: SingletonTest {
struct Singleton {
static let instance = SingletonTest()
}
return Singleton.instance
}
}
swiftSharedInstance can not be reached.
Nicky Goethlis's answer is correct but I just want to add another way of Singleton creation termed as One line Singleton" in Swift which I came across recently and it does not use Struct:
Singleton.swift
#objc class Singleton: NSObject {
static let _singletonInstance = Singleton()
private override init() {
//This prevents others from using the default '()' initializer for this class.
}
// the sharedInstance class method can be reached from ObjC. (From OP's answer.)
class func sharedInstance() -> Singleton {
return Singleton._singletonInstance
}
// Some testing
func testTheSingleton() -> String {
return "Hello World"
}
}
SomeObjCFile.m
Singleton *singleton = [Singleton sharedInstance];
NSString *testing = [singleton testTheSingleton];
NSLog(#"Testing---> %#",testing);
Swift 5 and above
final class Singleton: NSObject {
#objc static let shared = Singleton()
#objc var string: String = "Hello World"
private override init() {}
}
use in Objective-C
#import <ProjectName-Swift.h> // change ProjectName to actual project name
NSLog("Singleton String = %#", [Singleton shared].string);
For now I have the following solution. Maybe I am overlooking something that would enable me to access "swiftSharedInstance" directly?
#objc class SingletonTest: NSObject {
// swiftSharedInstance is not accessible from ObjC
class var swiftSharedInstance: SingletonTest {
struct Singleton {
static let instance = SingletonTest()
}
return Singleton.instance
}
// the sharedInstance class method can be reached from ObjC
class func sharedInstance() -> SingletonTest {
return SingletonTest.swiftSharedInstance
}
// Some testing
func testTheSingleton() -> String {
return "Hello World"
}
}
Then in ObjC I can get the sharedInstance class method (after importing the xcode generated swift header bindings)
SingletonTest *aTest = [SingletonTest sharedInstance];
NSLog(#"Singleton says: %#", [aTest testTheSingleton]);
To make members of the SingletonTest class accessible (swiftSharedInstance is a member of this class), use #objcMembers modifier on the class, or add #objc modifier directly on the swiftSharedInstance:
#objc #objcMembers class SingletonTest: NSObject {
// swiftSharedInstance is not accessible from ObjC
class var swiftSharedInstance: SingletonTest {
struct Singleton {
static let instance = SingletonTest()
}
return Singleton.instance
}
}
Or:
#objc class SingletonTest: NSObject {
// swiftSharedInstance is not accessible from ObjC
#objc class var swiftSharedInstance: SingletonTest {
struct Singleton {
static let instance = SingletonTest()
}
return Singleton.instance
}
}
After creating the Bridging header, be sure to have the Objective-C Generated Interface Header Name set in your Build Settings from your app target. If the value is empty, add the following value:
$(SWIFT_MODULE_NAME)-Swift.h
You need add #objc property wrapper to your singleton:
#objc final class Singleton: NSObject {
#objc static let sharedInstance = Singleton()
#objc func foo() { }
}
Then, in the Objective-C class, import the following:
// Replace the "App" with your Target name.
#import "App-Swift.h"
Finally, after compiling the project, you will be able to use your singleton from Swift inside your Objective-C class:
[[Singleton sharedInstance]foo];
You pretty much have it. To use Swift classes in Obj-C you both need to #import "SingletonTest-Swift.h the generated header or forward declaration with #class MySwiftClass.
Additionally the class needs to inherit from an Obj-C class like you have don here with NSObject or be marked with #objc to expose it. You don't need to do both though, #objc is there to be a more granular option when choosing things to expose.
Apple has some good documentation on all of this and there are two different WWDC sessions you can watch on the topic of Obj-C interoperability as well.
Don't forget to set sharedInstance as public
public final class TestSwiftMain: NSObject {
#objc public static let sharedInstance = TestSwiftMain()
private override init() {}
#objc public func test() {
print("testing swift framework")
}
}
Using it in Objc
[[testSwiftMain sharedInstance] test];
Update 12 Oct 2022
ObcMember So you won't have to write objC behind every function
Swift Class
#objcMembers class SwiftHelpingExtentions: NSObject {
static let instanceShared = SwiftHelpingExtentions()
func testingMethod() {
print("testing")
}
}
}
On objective C View Controller
import : #import "App-Swift.h"
Call The method:
[SwiftHelpingExtentions.instanceShared testingMethod];