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kotlinlang

Hey guys!

I am currently converting some java code to kotlin for my app and i have a question regarding Callbacks vs Closures. 

My java code uses a callback: 
Ex: 
```
public interface Callback {
   void onSuccess(Class item);
   void onError(Error error);
}
```

I was thinking of replacing this callback with a closure instead and my question is if it is better to add two closure parameters or to just have one? Is there a best practice for this?

Ex: 
```
onSuccess: (item: Class) -&gt; Unit, onError: (error: Error) -&gt; Unit
OR
callback: (item: Class, error: Error) -&gt; Unit
```
/Thanks

I don’t think there is universal “better” answer. Sometimes you might want to use Java-like listeners and anonymous objects, sometimes two lambdas, may be `sealed` hierarchy and single lambda with a `Result` parameter, or even a DSL builder for complex cases. Mostly it depends on how often do you use this event source: if it’s only couple of places, choose whatever is simpler. If it’s public facing API and/or there are many places you subscribe to the event then you might want to invest a little into usability.

Ok, then i’ll play around with closures and see what better fits my purpose :slightly_smiling_face:
Thanks