Re: Creating an array of default-constructed class instances

[Jos van Uden]

On 10-2-2013 7:14, Simon wrote:

Hi, I'm new to the D programming language.  Overall I'm liking
things very much, but I'm still getting the hang of a few things.

Here's a basic programming pattern: I have a class called Thing,
and while I'm coding I decide I need N Thing instances.

In C++ that's a matter of

std::vector<Thing> things(N);

In python, I can use a list comprehension.

things = [Thing() for _ in range(N)]

However, the obvious D version doesn't work.

auto things = new Thing[N];

Because Thing.init is null, this produces an array of null
references.  Of course, I can write a for loop to fill in the
array after creation, but this feels very un-D-like.  Is there a
straightforward way to create a bunch of class instances?

import std.stdio, std.algorithm;

class Thing {
    int i;
    this(int i) {
        this.i = i;
    }
}

void main()
{
   auto things = new Thing[10];
   fill(things, new Thing(5));

   foreach (t; things)
        writef("%d ", t.i);
}