I'm trying to achieve the syntax "opts[...] = 123", rather than using the more direct "this[...] = 123". I can use this code:

-----
class C
{
    this()
    {
        opts = Opts(this);
        opts["foo"] = 1;
    }

    struct Opts
    {
        C c;

        void opIndexAssign(T)(T value, string option)
        {
            c.assign(option, value);
        }
    }

    Opts opts;

    private void assign(string option, int value)
    {
    }
}

void main()
{
    auto c = new C();
}
-----

But this explicitly stores the 'this' reference in the struct, I was wondering if anyone knows of a trick to avoid having to do that. As you can tell I just want a more convenient operator-based syntax over calling the 'assign' method, but I don't want the operator to live in the class space itself (because then I'd have to use "this[...] = that", which is a little quirky for my taste).

On 08/31/2013 03:07 AM, Andrej Mitrovic wrote:

> I'm trying to achieve the syntax "opts[...] = 123", rather than using
> the more direct "this[...] = 123". I can use this code:
>
> -----
> class C
> {
>      this()
>      {
>          opts = Opts(this);
>          opts["foo"] = 1;
>      }
>
>      struct Opts
>      {
>          C c;
>
>          void opIndexAssign(T)(T value, string option)
>          {
>              c.assign(option, value);
>          }
>      }
>
>      Opts opts;
>
>      private void assign(string option, int value)
>      {
>      }
> }
>
> void main()
> {
>      auto c = new C();
> }
> -----
>
> But this explicitly stores the 'this' reference in the struct, I was
> wondering if anyone knows of a trick to avoid having to do that. As
> you can tell I just want a more convenient operator-based syntax over
> calling the 'assign' method, but I don't want the operator to live in
> the class space itself (because then I'd have to use "this[...] =
> that", which is a little quirky for my taste).
>

This is the limitation of inner structs' not having an 'outer' reference, right?

Even if that were automatically available, it would still need a reference similar to your explicit 'c' reference. I think... :)

Ali

On 9/1/13, Ali Çehreli <acehreli@yahoo.com> wrote:
> This is the limitation of inner structs' not having an 'outer' reference, right?

Right, but this was just a workaround. Anyway I did just realize I can use opDispatch for this:

-----
class C
{
    this()
    {
        this.opts["foo"] = 1;
    }

    private auto opDispatch(string field : "opts")()
    {
        return this;
    }

    private void opIndexAssign(T)(T value, string option)
    {
        assign(option, value);
    }

    private void assign(string option, int value)
    {
    }
}
-----

It might seem a little funny that the only thing it does is just returns 'this', which we already had. But I wanted to avoid writing 'this["foo"] = 1;'. Well at the end of the day this may or may not be what I wanted, since I still want to hide opDispatch. Oh well.. :)