Here's how I do it:
enum Dump; // just a type, no value here
template Dumper(T) {
void dump() {
foreach (mem; __traits(allMembers, T)) {
// loop over the attrs instead of try to store them in a
var
foreach(attr; __traits(getAttributes, __traits(getMember,
T, mem)))
// identify them by type rather than value
static if ( is(attr == Dump)) {
writeln(mem);
}
}
}
}
Or some helper functions might be good. Here's the ones I did:
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;
}
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;
}
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;
}
hasAnnotation!(something, Dump) tells you if it is just there
hasValueAnnotation tells you if the annoation has a value (enum
Dump; won't, but struct Dump { int option; } would).
getAnnotation fetches the value.
The "something" argument there is a symbol, e.g.
__traits(getMember, T, mem). The second argument is the type
you're interested in.
