In TypeScript there is a `Pick` type which lets yo...

# announcements

[vlad.minaev]

In TypeScript there is a Pick type which lets you easily (and type-safe) define sub-shape:

interface Todo {
    title: string;
    description: string;
    completed: boolean;
}

type TodoPreview = Pick<Todo, 'title' | 'completed'>; // you can only specify properties of Todo here

const todo: TodoPreview = {
    title: 'Clean room',
    completed: false,
};

I'm trying to find out whether it's possible to achieve something like this in Kotlin

[karelpeeters]

Not really, but you can define interfaces and separate data classes of course.

[tddmonkey]

a sealed class hierarchy might achieve what you want

[vlad.minaev]

not the case, I want to use java classes as source

[tddmonkey]

I’m not sure I follow then

[vlad.minaev]

see the example in the chat

[tddmonkey]

You could create your own builder for it then

[tddmonkey]

But you could also mirror your types in a sealed class hierarchy to achieve it

[tddmonkey]

Or write an annotation processor

[vlad.minaev]

yep, I cannot find anything better then annotation processor

[vlad.minaev]

still not clear how to make compile time property check

[Alowaniak]

I'm not sure if a Pick-like construct is very useful in a non-structural typing system though?

[vlad.minaev]

I brought it just to demonstrate property referencing