Object arrays in D

[simendsjo]

On Tue, 10 Apr 2012 13:58:44 +0200, CrudOMatic <crudomatic at gmail.com>  
wrote:

> Sorry, but a small issue.
>
> the line: auto card = cards.popBack();
>
> throws the errors:
>
> error: variable xxx.card voids have no value
> error: expression popBack(this.cards) is void and has no value
>
> I tried reserving the space, I even tried cards = new Card[no_cards];

Sorry, popBack returns void. You have to get the back of the array before  
calling popBack(). Here's an example:

import std.array;
class Card {}
void main() {
     Card[] cards;
     cards.reserve(1024);
     assert(cards.capacity >= 1024);
     assert(cards.length == 0); // still 0

     cards ~= new Card(); // add a Card
     assert(cards.length == 1);

     auto card = cards.back; // get last element
     cards.popBack(); // remove last element
     assert(card); // non-null
     assert(cards.length == 0); // "empty" again
     assumeSafeAppend(cards); // allow us to append to it without  
reallocating

     auto oldptr = cards.ptr;
     cards ~= new Card();
     assert(cards.length == 1);
     assert(card); // card still alive and kicking
     assert(cards.ptr == oldptr); // and no reallocation
}