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Is there a way to access a private member variable... so that to the user of the class it seems just to be a public const... but in actually fact its just a private member...
For example...
class X { // this class definition doesnt compile... just
private: // the best way to see what i am talkin about
int y;
public:
int y() { return this->y; }
};
X z;
cout << z.y; // this would display the contents of X::y.
z.y = 4; // this would be an error.
You don't need this->y -- just use y, since it assumes they'll be part of this.
Code:class X {
public:
int y() { return m_y; }
private:
int m_y; // it's a good idea to prefix member variables
};
X z;
cout << z.y(); // it's a function call so you need the brackets
z.y() = 4; // this would be an error (obviously ;))
Couldn't you use a member function to yield a pointer to the variable? Or actually, even better, a reference:
Code:class X {
public:
int& y() { return m_y; }
private:
int m_y; // it's a good idea to prefix member variables
};
X z;
cout << z.y(); // it's a function call so you need the brackets
z.y() = 4; // would this still be an error?
Seems to work fine. This compiled and ran as expected:
Code:#include <iostream>
class X
{
public:
int& y() { return m_y; }
X() { m_y = 2; }
private:
int m_y;
};
X z;
int main()
{
std::cout << z.y() << std::endl;
z.y() = 4;
std::cout << z.y() << std::endl;
return 0;
}
You could, but I think what he wanted was just to get the value...although returning a const reference is probably better if your class has a member variable that's a class/struct to prevent excess copying.
Uhh maybe I'm having a blonde moment... why would that prevent excess copying?
Okay...if it returns a value, it copies it. If it returns a reference, it doesn't copy it. However, returning a reference means you can change it, which isn't wanted. Therefore you return a const reference.
Ohh I was having a blonde moment. I didn't really understand what you were saying, I was thinking of the sentence in a different context.
I take the point about the const thing, I forgot it was meant to be const.
Heh, yeah I just realised what you were talking about before you posted :) I thought you meant a const reference was better than a normal reference because it prevented copying... that's what confused me.
No problem...just a tad confusing :(
I suppose it's random things like this they want to fix in the new standard.
I guess so. Have you heard anything specific about what they're looking at introducing? I read some general stuff but don't remember much of it.
Nothing specific, but according to those notes they're taking out the parts that confuse people.
Heh, why didn't they think of that sooner? :rolleyes: