Object arrays in D

[simendsjo]

On Tue, 10 Apr 2012 09:41:28 +0200, CrudOMatic <crudomatic at gmail.com>  
wrote:

> The D documentation is a little lacking in a lot of areas. I'm needing  
> to know an exact way of making arrays of objects.
>
> For example:
>
> /* Deck class */
> 	// Will be adjusted with the proper cards for each game type
> 	class Deck {
> 		/* Card count - used to keep track of how many cards are left in the  
> deck - when zero, Deck is discarded from the Shoe */
> 		int cardCount;
> 		/* Cards array - initialized to cardCount elements */
> 		Card cards[];
> 		
> 		/* Constructor */
> 		this(int no_cards) {
> 			cardCount = no_cards;
> 			cards = new Card[cardCount];
> 		}
> 		
> 		/* Destructor */
> 		~this() {
> 			delete cards;
> 		}
> 	}
>
> the cards[] array is meant to be an array of Card objects, and I'm  
> initializing it in the constructor as seen above. This hasn't been  
> tested yet, but I'm needing to know if this is the correct way of doing  
> it - to save headaches later.
>
> Also, while I'm here, how would you go about moving objects from the  
> cards array in the Deck class to another class containing a cards array  
> - I'm talking about MOVING them, not COPYING them. I don't want any  
> issues with references being destroyed after being moved to another  
> class when I happen to destroy an instance of the Deck class.

In D, arrays includes the number of elements in the array.

Card[] cards;
assert(cards.length == 0); // Automatically initialized to 0 elements
cards.length = cardCount; // cards gets cardCount of null elements
cards.reserve(cardCount); // This just extends the array without filling  
with null elements. cards.length stays at 0

D includes array slices - a view into an array. This way, you can  
reference cards without copying them.
auto other = cards[1..$-1]; // all but first and last card

I'll let someone else answer the moving part as I'm not sure how that  
could be done.

The delete statement is going away. You should use clear(cards) instead.  
This really isn't needed as Ds GC will take care of it eventually.

Your example could be written as

class Deck {
   Card[] cards;
   @property int cardCount() {
     return cards.length;
   }
   this(int no_cards) {
     cards.reserve(no_cards);
   }
}

Arrays are more complicated than they seem at first. I recommend you read  
this article: http://dlang.org/d-array-article.html

D has a newsgroup, .learn, for beginner questions.