Function that returns object name in c++

[ejjunju]

I want to initialise an object say A of class alphabet. the data for the object is located in a textfile A.txt.

How can I write a function in c++ that returns the name of the object as a char[] or string that I can manipulate into a filename, i.e. return char filename[]=A if the Object name is A.

How would this be possible also for Object arrays?

[firedraco]

You can't just "get" a variable/class/structs name, you will probably have to add a variable that stores its name inside the class/struct.

[Mal Reynolds]

firedraco is right, my first thought is that since you can initialize strings in c++ as such:

char szClassName[] = "CustomObjectClassName";

...put the preceding line of code in the "whateveryourclassis.c" file, but out of the scope of the class itself. this way, other files can't access it, but you can put a method in the ".c" file similar to this:

// pretend this is your header file
class customClass
{
public:
char* getClassNameString(void);
}
//____end header file________________ 

// this is your ".c" file
#include <yourheader.h>

char szClassName[] = "customClass\0";

char* customClass::getClassNameString(void)
{
return szClassName;
}

//______end .c file__________________ 

...i shouldn't, but i forget if the '\0' at the end is necessary to make it null terminated, i don't believe it is, but i'm not sure. I should know, but i also believe that by just returning szClassName that it will actually return a pointer to the first character in the string, but again, it's been a little while, so you might want to check.

[exception]

You can use rtti (run-time type information), namely typeid(x).name(), where x is an object of the type in question. However, the output is implementation-defined and is most likely tangled (C++ implementations use tangling to make unique function names from sets of overloaded functions and functions of the same name contained in different classes/namespaces). So to untangle them you have to read the documentation of your compiler. Also note that, following from that, this is non-portable, so perhaps the solution suggested above is better if at all applicable.

[jsmith]

If your compiler supports the __PRETTY_FUNCTION__ macro, then you can do this:

#include <iostream>
#include <string>

template< typename Derived >
struct NamedObject {
    NamedObject() : objName( __PRETTY_FUNCTION__ ) {}
    std::string ObjectName() const { return objName; }
  private:
    std::string objName;
};

class D: public NamedObject<D> {};

int main() {
    D d;
    std::cout << d.ObjectName() << std::endl;
}

Outputs on my machine:

NamedObject<Derived>::NamedObject() [with Derived = D]

Just need to parse out the text after the equal sign.

[exception]

Wow, I never heard about that macro before... Do you know how wide-spread it's implementation is?

[jsmith]

I think it is GCC-specific (which is why I started my statement "If your compiler supports..."). :)

[ejjunju]

Thanks for the advice but i guess my compiler cant handle. this is the result:
1>------ Build started: Project: HBV_Jjunju, Configuration: Debug Win32 ------
1>Compiling...
1>objectname.cpp
1>c:\hbv_jjunju\hbv_jjunju\objectname.cpp(6) : error C2065: '__PRETTY_FUNCTION__' : undeclared identifier
1> c:\hbv_jjunju\hbv_jjunju\objectname.cpp(6) : while compiling class template member function 'NamedObject<Derived>::NamedObject(void)'
1> with
1> [
1> Derived=D
1> ]
1> c:\hbv_jjunju\hbv_jjunju\objectname.cpp(12) : see reference to class template instantiation 'NamedObject<Derived>' being compiled
1> with
1> [
1> Derived=D
1> ]
1>Build log was saved at "file://c:\HBV_Jjunju\HBV_Jjunju\Debug\BuildLog.htm"
1>HBV_Jjunju - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

[jsmith]

No, because you are using a microsoft compiler.

So you'll either have to look a msoft documentation and see if they have an equivalent or use exception's idea of RTTI (the name will be mangled in this case).

[ejjunju]

will surely try again. thanks