Re: Mimicking Javas static class initializer in C++
Andreas Wollschlaeger wrote:
Lars Tetzlaff schrieb:
Andreas Wollschlaeger schrieb:
Hi folks,
as the subject says, i'm a poor Java programmer trying to transfer some
of his wisdom into C++ world... here is what im trying to do this
evening:
Java has a nifty feature called a static class initializer - something
like this:
You do not need to allocate every object with new in C++, so if you only
need a vector of Thing, use xx. If you need to allocate Thing on the
heap, use yy;
xx.h:
#include <vector>
class Thing
{
};
class Foo
{
private:
static std::vector<Thing> xx;
static class MyVector : public std::vector<Thing*>{ public:
MyVector(); } yy;
};
xx.cpp:
#include <xx.h>
std::vector<Thing> Foo::xx( 42 );
Foo::MyVector::MyVector()
{
for( int i = 0; i<42; ++i ) {
yy.push_back( new Thing() );
}
}
Foo::MyVector Foo::yy;
Well, great, this was just what i have been looking for: encapsulating
the statics initialization in some inner class and its default
constructor - much more elegant and "cplusplusish" than my previous
attempt :-) Tx to you and the other folks, added me some more insight to
C++ this evening!
I can see why that solution would look nice to a Java developer, but in
general, it's a bad idea to derive your own classes from the standard
ones; it is especially non-c++ish.
C++ methods aren't virtual by default; they're more like final methods
in Java. In particular, their destructors aren't virtual, so if ever an
instance of a derived type is deleted through a pointer to a base with a
non-virtual destructor, nasty things will happen. You're much better
off in this case with Victor or Juha's solutions, both of which are fine.
FWIW, most should-be-simple things aren't as complicated as this; there
are just a few "don't do thats" that you have to pick up when you get
started, and you happen to have gotten some mediocre advice (no offense,
Lars) right off the bat.