On Mar 26, 2013, at 14:14 , Conrad Shultz <conrad_shu...@apple.com> wrote:
> Step #1 in my hypothetical was that in the future a *required* delegate
> method be added, in which case there would be no -respondsToSelector: check.
1. Your earlier suggestion of having *two* delegate objects would certainly be
one way of ensuring this couldn't be a problem.
2. If there is to be only one delegate object, the correct way (in terms of
ensuring compile-time compliance) would be to declare the subclass "delegate"
property override like this:
@property (nonatomic) id<TKOutlineViewDelegate> delegate; // making it
readwrite now
That is, any code setting a delegate would be required to provide one of the
correct sort. If desirable (and perhaps it would be under the circumstances),
this could be enforced at run-time by providing overrides, rather than using
@dynamic:
- (id<TKOutlineViewDelegate>) delegate {
id<TKOutlineViewDelegate> delegate = [super delegate];
if ([delegate conformsToProtocol: @protocol
(TKOutlineViewDelegate)])
return delegate;
else
return nil;
}
- (void) setDelegate: (id<TKOutlineViewDelegate>) delegate {
NSAssert ([delegate conformsToProtocol: @protocol
(TKOutlineViewDelegate)], @"Boo boo");
[super setDelegate: delegate];
}
3. With one delegate object, if there's a legal scenario where some code might
think that the outline view was merely a NSOutlineView and therefore set a
delegate that was merely NSOutlineViewDelegate rather than
TKOutlineViewDelegate, then conformity to TKOutlineViewDelegate is effectively
optional. It would be incumbent, then, on callers of the TKOutlineViewDelegate
delegate methods to either check for conformity or to check respondsToSelector,
even for @required methods.
The correct approach requires knowing the answer to this question: Does
TKOutlineView *require* TKOutlineViewDelegate conformity, or is it merely
optional?
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