Interface analog in Swift for callbacks realization

Question

Please, help me to make interface in Swift to use it for callbacks purposes.

Example in Java:

public interface ErrorListener {
    void onError(String errorMsg);
}

class SomeUiClass implements ErrorListener {

    public SomeUiClass () {
        SomeWorkingClass s = new SomeWorkingClass();
        s.setErrorListener(this);
        s.doSomething(true);
    }

    @Override
    void onError(String errorMsg) {
        System.out.println("Error msg: " + errorMsg);
    }
}

class SomeWorkingClass {

    ErrorListener listener;

    void setErrorListener (ErrorListener listener) {
        this.listener = listener;
    }

    void doSomething (boolean withError) {
        if (withError) listener.onError("Test error");
    }

}


//....
SomeUiClass ui = new SomeUiClass(); // prints: Error msg: Test error

So, I tried to use protocol in Swift for this purpose, but I didn't understand, how to use it properly.

Shehata Gamal · Accepted Answer · 2018-09-28 11:41:46Z

1

It would look like this in swift

protocol ErrorListener {
    func onError(errorMsg:String)
} 
class SomeUiClass : UIViewController ,  ErrorListener { 

    func onError(errorMsg:String)
        print("Error msg: ", errorMsg)
    }
}

class SomeWorkingClass : UIViewController{

    weak var listener:ErrorListener?

    func setErrorListener (listener:ErrorListener) {
        self.listener = listener
    } 
} 

let ui = SomeUiClass() // prints: Error msg: Test error

answered Sep 28, 2018 at 11:41

Shehata Gamal

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