TITLE: insisting on initialized data member declarations


[ I am not advocating this as necessarily a good design
  practice. I put it here only as a "trick" to be aware
  of. -adc ]


PROBLEM: Artyom@kansmen.com (Art Shelest)

Anyone has a handy technique for initializing class members in the 
constructor? For example:

class A
{
public:
   A();
private:
   int m_int;
   int m_long;
};

Currently I use 

A::A() 
{ 
   m_int = 0; 
   m_int = 0;
}

and have to remember to update constructor every time I add a new member to 
the class. I would like an easier alternative.


RESPONSE: jcoffin@rmii.com (Jerry Coffin), 11 Feb 96

template <class T>
class initialized {
	T value;
public:
	initialized() : value(0) {}
	operator T() { return value; }
	initialized &operator=(const T &other) {
		if (this != &other )
			value=other;
		return *this;
	}
};

class A {
	initialized<int> my_int;
	initialized<long> my_long;
public:
	A() {}
	void do_something() { 
		my_int = 10; 
		my_long = 20;
	}
};

This is probably most useful as a container for primitive types -- when
your define a class, if it makes sense to provide default values, that's
best done in the default ctor.  E.g:

class my_thing {
	sometype value;
public:
	my_thing(sometype initial_value = 0) : value(initial_value) {}
};

This allows tailoring the value(s) and type(s) used to those appropriate
to the class being initialized.