Re: Problem with pointers
"mlt" <asdf@asd.com> kirjutas:
"Paavo Helde" <paavo@nospam.please.ee> wrote in message
news:Xns9B8917575281Dnobodyebiee@216.196.109.131...
"mlt" <asdf@asd.com> kirjutas:
In a class App I pass a pointer to a function :
class App {
private:
Bob b;
Pop * p;
public:
void do() {
b.init(p)
// Use p for various stuff
}
};
class Bob {
typedef Pop P;
public:
void init(P * p) {
p = new P();
}
Here, p is a local variable, the caller does not see changes to its
value. What you need is either to return the new value so it can be
assigned to the p in the caller:
P* init() {
return new P();
}
or maybe pass the parameter by reference if return by value is not
suitable for some reason:
void init(P*& p) {
p = new P();
}
I thought that pointers were always passed as reference and never by
value.
Why should specifically pointers passed by reference? The only thing this
achieves is making it possible to reseat the pointer in the outer scope,
as in your example, and this makes the program more complicated and might
be a sign of a bad design.
It might be conceivable to pass larger objects themselves by reference
automatically (IIRC Java does exactly this), but for consistency and
clarity C++ does not do this either.
Paavo
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