class function declarations 2

[lordblood]

I'm a C programmer attempting to learn more about C++ programming. I've been looking at C++ header files to familiarize myself with class declarations. I understand a fair amount about how the class structure works but I'm trying to figure out this:

(from exception.h on a SUN Solaris workshop pro v4.2, just in case someone needs it)

class xmsg {
public:
xmsg( const char * );
virtual ~xmsg();

const char * why() const;
void raise();
protected:
xmsg();
const char * msg_;
};

Theres the class declaration. Now one particular function definition I have a question. Can someone explain to me the following function? I understand the inline part and its a protected constructor, but the ": msg_(0)" part has me confused.

inline xmsg::xmsg()
: msg_(0)
{
}

If you need more information, let me know.

Thanks in advance.

 

[palbano]

That is the Initialization List of the constructor. The primary feature of this is to call base class and/or member constructors for initialization.

http://www.bridgespublishing.com/articles/issues/9902/Constructor_initializer_lists.htm

-pete