Make ListSerializer() a function on an object like serializer()

What is your use-case and why do you need this feature? Hey,

I just migrated to 1.0.0-RC and had to change my list serializations from MyClass.serializer().list to ListSerializer(MyClass.serializer()). I thought ListSerializer is a class and I need to create an instance of it, but it’s actually a method, what’s quite confusing.

I think this new solution is quite hard to find, if you don’t know it exists.

Describe the solution you’d like I’m wondering why it’s not simply MyClass.listSerializer() or just like before MyClass.serializer().list()? You can add similar methods for Sets and Maps. It’s way more straight-forward to understand and is consistent with how you use the “default” serializer.

[tom5079]

I think the reason behind the change is to follow the philosophy of object-oriented programming.

serializer.list implies that the single object serializer has a list serializer as a member of it, which sounds somewhat weird. ListSerializer(serializer) implies that the list serializer is containing a single object serializer, and it sounds more plausible.

I thought ListSerializer is a class and I need to create an instance of it, but it’s actually a method, what’s quite confusing.

You could think of it as a class constructor, indeed it is.

public fun <T> ListSerializer(elementSerializer: KSerializer<T>): KSerializer<List<T>> =
    ArrayListSerializer(elementSerializer)

calling a class constructor and top-level method is no different in Kotlin so where is your confusion coming from?

[Syex]

You can just write format.encodeToXxx(data) where data is of List<MyClass> type, and the appropriate serializer will be instantiated automatically

That’s pretty neat. Seems for me then it was only a migration issue.

Thanks for your explanation, very helpful, closing it then 👍