But what I meant is:
How do I implement it?
What does it mean?
Here's what I think you're asking:
1. I have class Blarf (with files Blarf.m and Blarf.h).
2. Somewhere I create an instance Blarf *myBlarfA.
3. I want myBlarfA to create a myBlarfB with a URL that myBlarfA knows.
If so:
Create an instance variable NSURL *myURL in class Blarf.
Use @property or write your own setters and getters.
In step 3 above, either:
myBlarfB.myURL = the special URL;
or
[myBlarfB setMyURL] = the special URL;
To confuse things more, if you don't have a myBlarfB, maybe you want:
[self setMyURL] = the special URL;
But the other guy's suggestion is probably better - if you're new to Cocoa, Objective-C and OOP, then grab a book and work through a couple of chapters.