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digitalmars.D.learn - Any trick for defining an operator overload in a different namespace?

reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
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).
Aug 31 2013
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
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
Aug 31 2013
parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 9/1/13, Ali =C7ehreli <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"] =3D 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"] =3D 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.. :)
Aug 31 2013