On 2013-04-16 08:29, Ulf Johansson wrote:
I have a question regarding using a struct value as user-defined
attribute. The use-case I am trying to get working is as follows:

struct message {
     int atom;
}

...

class AnActor : ... {
     @message(id) void myHandler(string arg1, real arg2) {
     }

     mixin ... // a mixin that builds message dispatch
}


The 'message' attribute defines methods of the class that will
participate in message dispatch argument matching. This works fine but I
want to take this one step further. I want to be able to give a message
and a handler an ID that more strictly directs a message (and gives an
error if arguments does not match).

The problem I have is quite simple - getting the value of 'atom' out of
the message attribute. How can I do this? I did not post any of my
actual code, I hope the above example describes the problem.

Regards,
Ulf

Use __traits(getAttributes, symbol) to get the attributes out of the given symbol. It will return a tuple with the attributes.

I would guess it would look something like this:

message msg = __traits(getAttributes, AnActor.myHandler)[0];
int atom = msg.atom;

See the docs:

http://dlang.org/traits.html#getAttributes
http://dlang.org/attribute.html#uda

--
/Jacob Carlborg

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