Get attribute by name

Question

I have a struct definition with about 25 elements

struct X { field 1; field 2; .. };    

and I'm trying to fill it with some map values

Map<String,String> A    

and it appears to be very annoying to do such thing n times

X->xx = A["aaa"]    

every time that I want to fill my message struct.

Is it possible to access the members by name, e.g.

X->get_instance_of("xx").set(A["aaa"]);    

and put it into a loop?

Answer 1

C++ lacks built-in reflection capabilities of more dynamic languages, so you cannot do what you would like using he out of the box capabilities of the language.

However, if all members are of the same type, you can do it with a map of pointers to members and a little preparation:

 // typedef for the pointer-to-member
 typedef int X::*ptr_attr;

 // Declare the map of pointers to members
 map<string,ptr_attr> mattr;
 // Add pointers to individual members one by one:
 mattr["xx"] = &X::xx;
 mattr["yy"] = &X::yy;

// Now that you have an instance of x...
 X x;
// you can access its members by pointers using the syntax below:
 x.*mattr["xx"] = A["aa"];

Answer 2

Short answer: no. This is C++, a statically compiled language, where the structure member names are converted by the compiler into memory offsets. It is not dynamic like PHP or Python where the runtime is involved with all variable references.