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: 
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.
You could create a wrapper objet for your struct with set/get accessors that will let you iterate over string values for filling/reading the underlying struct that is static.