Steven Schveighoffer wrote:
"Morusaka" wrote
Hi,
I've read about opdot in D language spec operator overload section, but
the little snippet of code provided isn't enough, for me, to figure out
what it is supposed to do and how to use it or what it could be usefull
for.
Could you please help me to get the right way?
opDot is useful if you want to make a 'wrapper' type. That is, you want to
mimic another type, but you want to slightly alter the behavior. opDot
allows you to 'inherit' all the member functions and fields from the wrapped
type. For example, if I wanted to create a wrapper type that added a
'blahblah' integer to the type, I could do this:
struct AddBlahBlah(T)
{
T _t;
int blahblah;
T *opDot() { return &_t;}
}
Now, if I declare an AddBlahBlah!(C) and class C has a member foo():
C c;
AddBlahBlah!(C) abb = AddBlahBlah!(C)(c);
abb.foo(); // translates to abb.opDot().foo()
abb.blahblah = 5; // sets abb.blahblah to 5, doesn't affect _t
Wow. That's incredibly useful for doing decorators!
http://en.wikipedia.org/wiki/Decorator_pattern
