How do I make my class iterable?

[Assembly via Digitalmars-d-learn]

On Monday, 22 June 2015 at 18:07:36 UTC, Ali Çehreli wrote:
> On 06/22/2015 10:03 AM, Assembly wrote:
>
> > foreach(int i, MyType p; places) {
> >
> > but I get this error:
> >
> > Error: cannot infer argument types, expected 1 argument, not 2
>
> Yeah, the loop counter is automatic only for slices. You can 
> use 'enumerate' for other types:
>
>     foreach (i, element; NumberRange(42, 47).enumerate) {
>         // ...
>     }
>
> That is taken from the same page: ;)
>
>
> http://ddili.org/ders/d.en/foreach_opapply.html#ix_foreach_opapply.loop%20counter
>
> Ali

if my opApply() is defiend as the following:

int opApply(int delegate(ref int, ref T) del)
	{
		int result;

		foreach(int i, T val; _app.data)
		{
			result = del(i, _app.data[i]);
			
			if(result)
				break;
		}

		return result;
	}

and called like:

foreach(int i, MyType p; places) {

isn't i the loop counter?