Introducing the iOS Responder Chain

Presented at Brisbane Cocoaheads, October 2015

Transcript

1. Introducing the Responder Chain Brisbane Cocoaheads Oct 2015 @lachlanroche
3. UIResponder • UIApplication • UIView (UIWindow) • UIViewController • SKNode • AppDelegate in a new project
4. UIApplication + sendAction:to:from:forEvent • This is what gets called when a wired up IBAction is triggered
5. to target: AnyObject? • “The object to receive the action message. If to is nil, the app sends the message to the first responder, from whence it progresses up the responder chain until it is handled.” • First Responder in IB means target == nil
6. “…from whence it progresses up the responder chain until it is handled.” • Initial receiver is the First Responder. • canPerformAction(_ action: Selector, withSender sender: AnyObject?) -> Bool • nextResponder() -> UIResponder?
8. Dismiss keyboard? • sendAction:@selector(resignFirstResponder) to:nil from:nil forEvent:nil
9. UITableViewCell • Works with UITableView to implement context menus. • If you want to send an action via the responder chain, override canPerformAction:withSender:
10. Finding First Responder static __weak id currentFirstResponder; @implementation UIResponder (FirstResponder) + (id) currentFirstResponder { currentFirstResponder = nil; [[UIApplication sharedApplication] sendAction:@selector(findFirstResponder:) to:nil from:nil forEvent:nil]; return currentFirstResponder; } - (void) findFirstResponder:(id)sender { currentFirstResponder = self; } @end