Hello all,
I can't seem to find an answer to this one, and I'm a little stumped. So I'm
reaching out to get a better understanding as to what is happening here. So I'm
building a small project which relies on OOP in Nim, and specifically the
inheritance aspect.
So take for example, I have the following classes/interfaces/what-have-you:
type
Application = ref object of RootObj
resources*: seq[Resource]
Run
type
Resource = ref object of RootObj
things*: seq[string]
method consume*(self: Resource) {.base.} = echo("Consumed!")
Run
Let's say the `Resource` parent has multiple base methods with default
implementations that can be overridden. And say I have the following
class/interface/what-have-you that inherits from `Resource`.
type
FoodResource = ref object of Resource
method consume*(self: FoodResource) = echo("Eaten!")
Run
So here is the start of the weird part that I don't understand. When I
instantiate an `Application`, and assign an instance of `FoodResource` to its
property `resources`, it will throw a type error... which I guess is fair,
given that `FoodResource` really isn't type `Resource`.
let food = FoodResource(
things: @["Apple", "Orange", "Pear"]
)
let app = Application(
resources: @[food]
)
Run
But when I create another class/interface/what-have-you that inherits from
`Resource` and assign an instance of that together with the instance of
`FoodResource` to `resources` property of the instance of `Application`, it
works.
type
FuelResource = ref object of Resource
method consume*(self: FuelResource) = echo("Guzzled!")
Run
let food = FoodResource(
things: @["Apple", "Orange", "Pear"]
)
let fuel = FuelResource(
things: @["Shell", "BP"]
)
let app = Application(
resources: @[food, fuel]
)
Run
So my question is, how does the shorthand initialisation of a sequence infer
it's internal types when mixed with classes/interfaces/what-have-you that
inherit from a parent? Why does it enforce the parent type `Resource` when
there is only one item in the sequence but will allow for inherited types when
there is multiple items in the sequence? I do hope this all makes sense.
