Re: Copy Constructor
On 2007-07-30 13:00, Roy wrote:
On Jul 30, 3:54 pm, Erik Wikstr?m <Erik-wikst...@telia.com> wrote:
On 2007-07-30 12:21, Roy wrote:
[snip]
continuing with the initialization list this code compiles okay and runs fine but does it create a memory leak ?
class x{
public:
char* getname(){return b}
x():b(NULL){}
x(acName):b(acName){}
~x(){}
private:
char* b;
};
main(){
x *a;
a=new x("ashish");
cout<<a->getname()<<endl;
delete a;
}
Kindly point out the errors in this code ?
You probably want to store a copy of the name, not just a pointer to it.
Consider what would happen if someone changed the text pointed to by b.
--
Erik Wikstr?m
Hmmm , Ok , so what should be the right way of doing it through an
initialization list ? should i use the String type instead of a
char* ?
The general advice is to always use string instead of char* so that's
probably a good solution. If for some reason you can't use string, you
can allocate the space in the initialisation list and copy the string in
the constructor body (or do both in the body).
You can't do everything in the initialisation list, it's only an
optimisation to prevent calling the default constructor on all members
before assigning them (and for some classes where default constructors
are not available they are necessary). Consider the following code:
#include <string>
class Foo {
std::string str;
public:
Foo(std::string& s) {
str = s;
}
};
int main() {
std::string text("Hello World");
Foo f(text);
}
What happens when f is created is that first f.str is constructed using
the default constructor, then the text "Hello World" is assigned to it.
If we use an initialisation list instead:
Foo(std::string& s) : str(s) {}
what happens is that f.str will be constructed with the text "Hello
World" directly and no assignment is needed.
In this example there's probably not much difference in execution speed
but if you run the code many many times, or if you have some other kind
of object, it can have quite a big impact.
--
Erik Wikstr?m