override '.' member access

[spir]

On 01/26/2011 12:05 AM, spir wrote:
> On 01/25/2011 10:29 PM, Simen kjaeraas wrote:
>> spir <denis.spir at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> Cannot find corresponding opSomething method, if any. (opDispatch seems to
>>> specialise for method call.)
>>> Else, how to catch obj.member?
>>
>> opDispatch is likely what you want. with the @property annotation, it
>> will readily support obj.member; and obj.member = foo; syntax.
>
> Thank you, Simen, i'll try using opDispatch with @property. But I'm not sure
> how to write that concretely. My use case is of a type holding a
> string[AnyThing] AA called symbols. Then, I wish to map
> obj.id
> to
> obj.symbols["id"]
> (hope I'm clear)
>
> Denis

Right, just understood that you meant, I guess: since D supports properties 
with "x.a" syntax mapping to a func call x.a() under the hood, then one can use 
opDispatch intended for func calls to dispatch plain data membar access. (woof!).
FWIW: the following works fine:

alias int[string] Symbols;

class T {
     int i;
     Symbols symbols;
     this (int i, Symbols symbols) {
         this.i = i;
         this.symbols = symbols;
     }
     auto opDispatch (string name) () {
         auto p = (name in this.symbols);
         if (p)
             return *p;
         throw new Exception("No symbol called "~name~".");
     }
}
unittest {
     auto t = new T(1, ["j":2, "k":3]);
     writeln(t.i);
     writeln(t.j);
     writeln(t.k);
     writeln(t.l);   // throws as expected
}


Denis
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