Closure-based gesture recognizers
In my previous post, I wrote about how I don’t like delegates and target/selectors and how I prefer closures. Let’s see how to use closures in gesture recognizers to make things nicer.
In my apps, I work around using delegates and target/selectors by adding action properties to my views. However, this requires me to add these properties to every view or create sub classes, which isn’t nice.
I have experimented with extensions, but since extensions can’t store data, I use protocols that ensure that I have closure storage properties, then extend the protocols with closure-based gesture functions. This requires me to implement the protocol for each view, though.
While neither approach is perfect, I still think that they are better than using delegates and selectors. I’d very much prefer Apple to add closure-based gestures.
Today, I found this article that describes how to use associated objects to let an extension store properties. With this, we can implement UIView extensions that add closure-based gesture recognizers to our views:
public extension UIView {
public func addLongPressGestureRecognizer(action: (() -> Void)?) {
longPressAction = action
isUserInteractionEnabled = true
let selector = #selector(handleLongPress)
let recognizer = UILongPressGestureRecognizer(target: self, action: selector)
addGestureRecognizer(recognizer)
}
}
fileprivate extension UIView {
typealias Action = (() -> Void)
struct Key { static var id = "longPressAction" }
var longPressAction: Action? {
get {
return objc_getAssociatedObject(self, &Key.id) as? Action
}
set {
guard let value = newValue else { return }
let policy = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN
objc_setAssociatedObject(self, &Key.id, value, policy)
}
}
@objc func handleLongPress(sender: UILongPressGestureRecognizer) {
guard sender.state == .began else { return }
longPressAction?()
}
}
public extension UIView {
public func addTapGestureRecognizer(action: (() -> Void)?) {
tapAction = action
isUserInteractionEnabled = true
let selector = #selector(handleTap)
let recognizer = UITapGestureRecognizer(target: self, action: selector)
addGestureRecognizer(recognizer)
}
}
fileprivate extension UIView {
typealias Action = (() -> Void)
struct Key { static var id = "tapAction" }
var tapAction: Action? {
get {
return objc_getAssociatedObject(self, &Key.id) as? Action
}
set {
guard let value = newValue else { return }
let policy = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN
objc_setAssociatedObject(self, &Key.id, value, policy)
}
}
@objc func handleTap(sender: UITapGestureRecognizer) {
tapAction?()
}
}
If this approach doesn’t turn out to use private api:s not approved by Apple, I believe that I’ve now found a perfect approach to not having to use delegates or selectors ever again.
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