Re: What's the different betteen pure virtual function and virtual
function
Juha Nieminen schrieb:
Lars Uffmann wrote:
Jack wrote:
I did not get clear the different betteen them,
Given there's no errors in the code below (am not familiar enough with
virtual to know for sure on all the calls), I can provide my input:
for example:
[..]
virtual ~Base();
virtual void pure() = 0;
inline void Base::pure()
{
std::cout << "Base::pure() called\n";
}
I think the pure() = 0 assignment in the class definition has no effect
since you later define the function, actually I'm not even sure if it is
allowed by the compiler.
Maybe you should familiarize yourself with pure virtual functions
before giving answers about things you don't know?
"virtual void pure() = 0;" is not an assignment. It's just a syntax
for declaring a pure virtual function (AFAIK the story of this goes
something like the C++ standardization committee not wanting to create
yet another reserved keyword for only this purpose).
"void" would be nice:
virtual void pure(void) void; // not serious!
It's perfectly valid to give a pure virtual function an
implementation. The function will still be purely virtual (ie. the class
must be inherited to instantiate it), but the implementation can be
called explicitly.
Just to add:
In one case, you _have to_ give an implementation: In a pure virtual
destructor. Since the destructor of a derived class will call all its
base class destructors recursively, you need an implementation for all
destructors, even for pure ones.
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