Hi everyone. I found something odd that seems baked into how Cocoa Touch does
protocols, but Swift cannot model it:
@interface UIScrollView: UIView
@property (weak, nonatomic) id <UIScrollViewDelegate> delegate;
@end
@interface UITableView: UIScrollView
@property (weak, nonatomic) id <UITableViewDelegate> delegate;
@end
@protocol UITableViewDelegate: UIScrollViewDelegate
...
@end
Subclasses can further specify the conformance of a property’s
protocol-conforming object to state a further type on that property. I tried to
do something extremely similar today in Swift, and it failed, saying the
protocols were different:
class SourceBar: UIScrollView {
override var delegate: SourceBarDelegate? {
get { return super.delegate as? SourceBarDelegate }
set { super.delegate = newValue }
}
}
@objc protocol SourceBarDelegate: UIScrollViewDelegate {
func foo()
}
Considering the fact that the protocol SourceBarDelegate conforms to
UIScrollViewDelegate, I can’t see why this override should fail. Can anyone
enlighten me as to why this is a limitation in the language?
Thanks,
Rod
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