On 10/04/2013 11:04 PM, Adam D. Ruppe wrote:
> On Saturday, 5 October 2013 at 02:51:21 UTC, Matt Soucy wrote:
>> * Check to see if a specific attribute exists
>> * Check to see if an attribute of a specific type exists, something like:
>
> The helper functions from my web.d might help:
>
> // checks to see if it has one of a type
> // static if(hasAnnotation!(func, Foo)) { has @Foo }
> // use if Foo is a simple enum.
> template hasAnnotation(alias f, Attr) {
> bool helper() {
> foreach(attr; __traits(getAttributes, f))
> static if(is(attr == Attr) || is(typeof(attr) == Attr))
> return true;
> return false;
>
> }
> enum bool hasAnnotation = helper;
> }
>
> /// checks to see if it has an annotation with a value e.g. @Something(10)
> template hasValueAnnotation(alias f, Attr) {
> bool helper() {
> foreach(attr; __traits(getAttributes, f))
> static if(is(typeof(attr) == Attr))
> return true;
> return false;
>
> }
> enum bool hasValueAnnotation = helper;
> }
>
> /// gets the thing you checked for above. so getAnnotation!(Func,
> Something) returns Something(10) (if Something is as struct)
> template getAnnotation(alias f, Attr) if(hasValueAnnotation!(f, Attr)) {
> auto helper() {
> foreach(attr; __traits(getAttributes, f))
> static if(is(typeof(attr) == Attr))
> return attr;
> assert(0);
> }
>
> enum getAnnotation = helper;
> }
>
> Nice, thank you. These are really helpful! >> * Create a function that can only be called if the first argument has a >> UDA of a specific type > > Since the UDA is only available at compile time, you can't do that > without some kind of template. Using the above tools I got what I wanted, so I'm satisfied for now. Thank you, though! -Matt Soucy
signature.asc
Description: OpenPGP digital signature
