How to use swift protocol implementation in Objective-C?

Question

I am new in iOS. I have a lib that I use in my App both in Swift and Objc files (I have connected my lib correctly including the *-Swift.h file).

So, my lib has such a structure

Factory

import Foundation

@objc public class Factory : NSObject{
    @objc public func create() -> ModelProtocol
    {
        return FirstModel()
    }
}

Model protocol

import Foundation

@objc public protocol ModelProtocol
{
    func foo()
}

First Model

import Foundation

public class FirstModel : NSObject, ModelProtocol
{
    public func foo() {
        //Do some things here
    }
}

when I try to use this factory on the Swift side everything is working properly

import Foundation
import Lib

class TestClass {
    
    public init(){}
    
    func boo()
    {
        let factory = Factory()
        let _: ModelProtocol = factory.create()
    }
}

but when I try to do the same on the Objc side I got an error

Use of undeclared identifier 'ModelProtocol'

#import <Foundation/Foundation.h>
#import "Lib-Swift.h"


@implementation ViewController : NSObject

- (void)foo {
    Factory *factory = [Factory new];
    ModelProtocol *protocol = [factory create];
}

@end

also I put both these projects (lib & app) on my drive https://drive.google.com/drive/folders/1-DMYMhTqTqpgHcp31DNVby7US46OXUYM?usp=sharing

How to fix it?

Sulthan · Accepted Answer · 2021-06-30 12:28:59Z

1

Actually your only problem is incorrect syntax of protocols in Objective-C. Correctly, a type conforming to protocol would be written this way:

id<ModelProtocol> protocol = [factory create];

answered Jun 30, 2021 at 12:28

Sulthan

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