Thoughts on __post_init__ like pattern?

Mojo
1

I love the @value decorator that generates __init__ methods for structs. Is there a pattern to support computed fields that are not initialized through input arguments?

For example in the struct below I would like to pass length, bitmap and buffers in the constructor but have _null_count default to -1. Then the _null_count will be initialized on the first call to the null_count() method.

@value
struct ArrayData(Movable, Writable):
    var length: Int
    var bitmap: ArcPointer[Bitmap]
    var buffers: List[ArcPointer[Buffer]]
    var _null_count: Int

In Python, with dataclasses, you could initialize _null_count to -1 during the field declaration.

I can of course write my own __init__ and friends, wondering if there is a way for me to be lazy.

Thanks!

Marius

2

For now I just implemented __init__ and friends. Initial implementation is trivial in our AI age, more of a concern for maintenance.