Passing struct and struct[] into a template

Taylor Gronka via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Tue Jul 21 21:29:23 PDT 2015


Hi,

I have a template function, and I want it to do something if the 
input variable is a list of structs, and something else if the 
input is a struct.

1) What's the best way to test this? I suppose I can call 
__traits(identifier, results) and look at the last two characters.
2) If `T` is a list of structs, how can I initialize a new struct 
so that I can append to `T`?

This is sort of how it might be done in python. I haven't 
implemented question 2 yet since I'm not sure how atm:

template Uks(T) {
     T query(string q) {
         T result;
         try {
             ulong test = result.length; // won't compile for 
non-list structs
             // append to a struct list
             T.subtype newResult; // is there a function like this?
             result ~= newResult;
         } catch {
             // assign the struct members directly
         }
         return result;
     }
}

I would like to call it like either of the following, depending 
on if I want 1 result or X results:
auto res = Uks!(U_Struct).query("email");
auto res = Uks!(U_Struct[]).query("email");

I'd be happy to hear better design methods.

Thanks


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