问题
I encountered a weird behavior. The best way I can put it is … Not overridden protocol methods in a class extension are not called while the superclass already conforms to the protocol (via extension). However this happens only while it's build with the release
build configuration.
class A: UIViewController {}
extension A: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
print("scrollViewDidScroll in superclass")
}
}
class B: A {
// A tableView (and its data source and delegate) is set here…
}
extension B: UITableViewDelegate {
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
super.scrollViewDidScroll(scrollView)
print("scrollViewDidScroll in subclass")
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
print("scrollViewDidEndDragging")
}
}
The output:
scrollViewDidScroll in superclass
scrollViewDidScroll in subclass
scrollViewDidEndDragging
however if I build it with the release
build configuration, the output is
scrollViewDidScroll in superclass
scrollViewDidScroll in subclass
I can solve the problem if I don't use the extension for protocol conformance approach in the class B
and just use the regular way instead (put the methods that implement a protocol into the class).
The question is … how come?
来源:https://stackoverflow.com/questions/56645685/protocol-methods-in-a-class-extension-are-not-called-under-specific-conditions