C++ - ostream, friends and namespaces - c++

Question

Everything was fine until I moved my objects to a namespace. And now the compiler claims that my Color attributes are private.
I thought the whole point of friends was to share encapsulated information with those a class befriends.
Color.h
friend ostream & operator << (ostream& output, const st::Color& color);
Color.cpp:
ostream & operator <<(ostream& output, const st::Color& color) {
output << "Colors:\nalpha\t: " << color.a << "\nred\t: " << color.r << "\ngreen\t: " << color.g
<< "\nblue\t: " << color.b << "\nvalue\t: " << color.color();
return output;
}
error:
Color.h||In function 'std::ostream& operator<<(std::ostream&, const st::Color&)':|
Color.h|52|error: 'unsigned char st::Color::a' is private|
Color.cpp|15|error: within this context|
Color.h|49|error: 'unsigned char st::Color::r' is private|
Color.cpp|15|error: within this context|
Color.h|51|error: 'unsigned char st::Color::g' is private|
Color.cpp|15|error: within this context|
Color.h|50|error: 'unsigned char st::Color::b' is private|
Color.cpp|16|error: within this context|
||=== Build finished: 8 errors, 0 warnings (0 minutes, 1 seconds) ===|
So what is the deal?
I'm using Code::Blocks as my IDE. And it won't even show any properties or methods when I use the dot operator on the "color" parameter. This is obviously a sign of something going wrong...somewhere.
I've taken the friend operator overloading out and it compiles just fine. No error elsewhere.
What gives?
It's declared as follows:
namespace st{
class Color {
friend ostream & operator << (ostream& output, const st::Color& color);
public:
....
private:
.....
};
};
Edit:
In my CPP I've now done this:
namespace st{
ostream & st::operator <<(ostream& output, const st::Color& color) {
output << "Colors:\nalpha\t: " << color.a << "\nred\t: " << color.r << "\ngreen\t: " << color.g
<< "\nblue\t: " << color.b << "\nvalue\t: " << color.color();
return output;
}
}
st::Color::Color() {
reset();
}
st::Color::Color(const Color& orig) {
a = orig.a;
r = orig.r;
g = orig.g;
b = orig.b;
}
void st::Color::reset() {
a = 0;
r = 0;
g = 0;
b = 0;
}
... etc
}
No compile errors, but is it normal for such a situation to use the namespace again in the header? Or is this completely off from what I should be doing?
Edit:
#Rob thanks for your input as well!

Answer 1

You need to declare and define your operators in the same namespace as the object as well. They will still be found through Argument-Dependent-Lookup.
A usual implementation will look like this:
/// header file
namespace foo {
class A
{
public:
A();
private:
int x_;
friend std::ostream& operator<<(std::ostream& o, const A& a);
};
std::ostream& operator<<(std::ostream& o, const A& a);
} // foo
// cpp file
namespace foo {
A::A() : x_(23) {}
std::ostream& operator<<(std::ostream& o, const A& a){
return o << "A: " << a.x_;
}
} // foo
int main()
{
foo::A a;
std::cout << a << std::endl;
return 0;
}
Edit
It seems that you are not declarin your operator<< in the namespace and are also defining it outside of the namespace. I've adjusted the code.

Answer 2

You need to qualify your operator with the namespace as well. It is a function signature declared in the name space so to access its symbol you need to prefix it with the namespace.
Try it like this:
namespace st {
ostream & operator <<(ostream& output, const Color & color) {
output << "Colors:\nalpha\t: " << color.a
<< "\nred\t: " << color.r
<< "\ngreen\t: " << color.g
<< "\nblue\t: " << color.b
<< "\nvalue\t: " << color.color();
return output;
}
}