On May 10, 2008, at 11:40 AM, Jens Alfke wrote:
On 9 May '08, at 7:41 PM, Chris Hanson wrote:
(6) Leverage Cocoa framework features in your own code. For
example, you don't need to have setter methods that invoke -
setDirty:. You can just write a method like this
- (NSSet *)keyPathsForValuesAffectingDirty {
return [NSSet setWithObject:@"UUID"];
}
and then anything that cares about whether a particular object is
dirty can observe its "dirty" property.
But you still need to implement the "dirty" property, with a getter
that returns the corresponding ivar; and the other setters like -
setUUID: need to set the ivar to true.
Not necessarily. You can simply return a constant YES for a read-only
"dirty" property, and treat the property-change itself as the trigger
you care about.
Even better, though, would be for code to observe only the properties
of the object that it actually cares about.
The question is, of course, why not just use Core Data if you're going
to be doing object-graph management? It's not a "beginner"
technology, but that is what it's for, and the original poster would
probably do well to take a look at it before going to far in the
direction of implementing a completely different object graph
management and persistence framework.
Plus, I'll bet the internal general-purpose dependency tracking is
less efficient than the hardcoded call to -setDirty.
You would be surprised. For example, in the above case, the
automatically-generated setters for the "bar" and "baz" properties may
only post a KVO notification for the "dirty" property if it's actually
observed.
There are a lot of things that can be done under the hood to be
efficient when you work declaratively instead of procedurally. Not
implementing accessors, and instead using declarative mechanisms like
KVO, is one of those cases where the system can really help you.
-- Chris
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