On May 19, 2009, at 20:39:12, Ken Thomases wrote:
On May 19, 2009, at 6:24 PM, Rick Mann wrote:
I have some key paths dependent on other paths. I'm using
+keypathsForValuesAffectingFoo to set up the dependency.
Now I have a chain of dependencies: A -> B -> C. Is it better to
just have B depend on C, and A depend on B, or should A explicitly
depend on B and C?
I would say that it should follow the implementation of property A.
Is property A implemented by directly using property C, or only
property B?
From a maintenance perspective, you don't want to introduce
dependencies where you don't have to. Somebody should be able to
reproduce +keypathsForValuesAffectingA by looking at -a and -setA:
and whatever other methods constitute the implementation of A.
Put another way, somebody changing the implementation (not the
interface nor contract) of B should not have to go around to all of
the properties that might depend on B and check how they were
written. B's implementation should be local to itself and should
not leak into the implementation of A.
That's a reasonable rule of thumb. In this case, A is implemented only
in terms of B, not C. Thanks!
--
Rick
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