On Tuesday, 11 June 2013 at 07:00:29 UTC, Jacob Carlborg wrote:
This was brought up in the thread reviewing std.serialization:
http://forum.dlang.org/thread/[email protected]
Currently we haven't started to use UDA's in Phobos or druntime
yet (as far as I know). I would like to start a discussion
about putting out some guidelines for using UDA's in
Phobos/druntime.
I've created a small module that handles UDA's:
https://github.com/jacob-carlborg/orange/blob/master/orange/core/Attribute.d
The idea is to have a kind of meta UDA called "attribute". This
attribute needs to be attached to all structs, enums and so on
that is to be used as an attribute.
The module provides a template (getAttributes) to get, by
default, only those values attached to a given symbol that is
an attribute. That is, marked with the "attribute" attribute.
So my suggestion for guidelines are:
* Only types with the "attribute" UDA is to be used as
attributes
* In general, don't use primitive values as a UDA
Don't use this
@(3) int a;
Use this:
@attribute struct foo { int b; }
@foo(3) int a;
* A user defined type marked with "attribute" should not be
used for something else than an UDA
* All attributes use camel case names
If we agree on this and that we need a module like the one
above I think it should be added to druntime. The reason for
that is that we most likely want to use UDA's in druntime and
not only in Phobos. Example, if we ever get std.serialization
into Phobos we would want to mark Thread and similar
structs/classes as "nonSerialized".
Thoughts?
I agree that attributes should have types - that way it's easily
recognizable what are they for in code. "Anonymous" attributes
seem to me to be sort of like "you can throw ANYTHING in c++"
feature - it's there, but probably without a sane use case.
Could you explain to me what's the benefit of the @attribute
convention you introduce? It seems non-obvious to me.
