On 08/03/2024 4:09 PM, Liam McGillivray wrote:
On Thursday, 7 March 2024 at 22:18:40 UTC, Richard (Rikki) Andrew
Cattermole wrote:
There are two ways to do this.
1. Use templates. https://tour.dlang.org/tour/en/basics/templates
2. Use a factory function.
https://tour.dlang.org/tour/en/basics/delegates
```d
class Map(ATile : Tile) {
ATile[] tiles;
}
```
Thank you. Is this first example you gave the template? Is the syntax
`(ATile : Tile)` saying that ATile must be a derived class of Tile? If
this isn't worse in any way than your second example, then I don't know
why I wouldn't choose this one.
Typically in D we use templates quite heavily, but what you are wanting
is probably more familiar to you via the OOP method with a factory of
some kind.
I suppose that if I do this, then the derived class `Mission` would be
declared like `class Mission : Map(GridTile)`, right?
``class Mission : Map!GridTile`` but right idea.
When I tried adding that parameter to the Map class, on attempting to
build it it complained that references to Map in other classes were
incomplete, as they didn't include a parameter. I suppose I must make my
other classes templates too.
Something strange that I just realized is that (without doing any of the
changes you suggested to me), I have a reference to a Map object as one
of the class variables in Unit, yet it has allowed me to place a Mission
object in it's place. It no longer allows me if I change it to a
pointer. Why is it sometimes possible to put a derived class in a place
meant for the class it inherits from?
That should always be allowed.
