nimforum mirror - Begginer's question

I'm still new to Nim (got it a couple of days ago).

Both versions work. Which one is better? (It is not clear, or I have missed something in docs.)

The first:

var sdl_rect : Rect
sdl_rect = ( (cint)0, (cint)0, (cint)10, (cint)10 )
# usage: (addr sdl_rect), when ptr Rect is required

The second:

var sdl_rect : ref Rect
new(sdl_rect)
sdl_rect.x = 0
sdl_rect.y = 0
sdl_rect.w = 10
sdl_rect.h = 10
# usage: sdl_rect, when ptr Rect is required

That is not an easy topic for a beginner, you may start with

var sdl_rect : Rect is better.

I disagree, at least regarding the question in the title.

A ref is always preferable unless one needs a pointer. And the heap vs. stack is not Nim specific.

In the example it's not a pointer though, it's a stack object (assuming Rect is a simple object).

Use var sdl_rect : Rect If you ate going to process a lot of them sequentially.

Use var sdl_rect : ref Rect If you only handle those instances individually or if you use OOP or if there is a lot of fields (data) in the object

@aguspiza, I think you are confused about mutability/immutability, var and ref.

var means mutable. ref means object on the heap with reference semantics. They are somewhat orthogonal concepts.

Yes you are right. I was thinking about type definiton while the question was about variable definition. Thanks.

Mirror of forum.nim-lang.org