Convert one function from java to kotlin android

Question

I have developed one app in JAVA. Now I have made one function for firebase related calls. and Working perfectly. But now I want to convert that function to kotlin also. But I was confused about how to use that function call in kotlin.

Function of Java :

public static void firebaseAuth(FirebaseAuth auth, AuthCredential authCredential, Function<Object, Void> delegate) {
    auth.signInWithCredential(authCredential).addOnCompleteListener(task -> {
        if (task.isSuccessful()) {
            delegate.apply(auth.getCurrentUser());
        } else {
            delegate.apply(task.getException());
        }
    });
}

Use of this Function in Java :

FireSignInHelper.firebaseAuth(mFireAuth, authCredential, o -> {

            if (o instanceof Exception) {
                signIn_UnSuccessful((Exception) o);
            } else if (o instanceof FirebaseUser) {
                FirePacket firePacket = new FirePacket();
                firePacket.setProvider(provider);
                firePacket.setToken(((FirebaseUser) o).getUid());
                firePacket.setFirebaseUser((FirebaseUser) o);
                signIn_Successful(firePacket);
            }
            return null;
        });

Converted Function In Kotlin :

fun firebaseAuth(auth: FirebaseAuth,
    authCredential: AuthCredential?,
    delegate: Function<Any?, Void?>
) {
    auth.signInWithCredential(authCredential!!)
        .addOnCompleteListener { task: Task<AuthResult?> ->
            if (task.isSuccessful) {
                delegate.apply(auth.currentUser)
            } else {
                delegate.apply(task.exception)
            }
        }
}

Use Converted function in kotlin:

I want to know this answer. Because I have try through Android studio but the compiler didn't convert properly. So I want to know how to use this function in kotlin.

Thanks In advance.

Kindly refer to this post to get an answer. stackoverflow.com/questions/34588117/… — Gabe
– Gabe, Commented Apr 5, 2020 at 18:42
I have already tried that but not converted properly. That's why I have posted it here. — ankur bhut
– ankur bhut, Commented Apr 5, 2020 at 18:44

Yann Huissoud · Accepted Answer · 2020-04-05 22:13:55Z

2

The way IntelliJ convert your code is correct. However the Function interface is of no use in kotlin since functions are first-class citizens. See higher-Order Functions examples from the doc.

I think you simply want to do something like this

fun firebaseAuth(
    auth: FirebaseAuth,
    authCredential: AuthCredential?,
    listener: (Any) -> Unit
) {
    auth.signInWithCredential(authCredential!!)
        .addOnCompleteListener {
            listener.invoke(
                if (it.isSuccessful) auth.currentUser 
                else it.exception
            )                
        }
}

And then

FireSignInHelper.firebaseAuth(mFireAuth, authCredential) { 
     when(it){
        is FirebaseUser -> { ... }
        is Exception -> { ... }
     }
}

edited Apr 5, 2020 at 22:13

answered Apr 5, 2020 at 18:46

Yann Huissoud

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4 Comments

ankur bhut Over a year ago

How can I use the this delegate: Function<Any?, Void?> third argument of function?

Yann Huissoud Over a year ago

Why would you? This Function<Foo, Bar> is the Java way of implementing callbacks or function pointers. My code show you the way of doing it in Kotlin.

ankur bhut Over a year ago

Okay I will try to do with your answer and keep you posted.

ankur bhut Over a year ago

Thank You Very Much.

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