UIViewController init
Actually UIViewController intialization is pretty straightforward. You only have to override a few methods if you want to be in full control. It depends on the circumstances which init will be called, if you are using a storyboard, init(coder) is the one that you are looking for. If you are trying to initiate your controller from an external nib file, init(nib,bundle) is going to be called. You also have a third option, you can initialize a controller programmatically from code. Long story short, in order to make a sane init process, you have to deal with all this stuff.
Let me introduce two patterns for UIViewControllers, the first one is just a common init function that gets called in every case that could initialize a controller.
import UIKit
class ViewController: UIViewController {
override init(
nibName nibNameOrNil: String?,
bundle nibBundleOrNil: Bundle?
) {
super.init(
nibName: nibNameOrNil,
bundle: nibBundleOrNil
)
self.initialize()
}
required init?(
coder aDecoder: NSCoder
) {
super.init(coder: aDecoder)
self.initialize()
}
init() {
super.init(nibName: nil, bundle: nil)
self.initialize()
}
func initialize() {
}
}You can also hide the init(nib:bundle) and init(coder) methods from the future subclasses. You don’t have to override init(nib:bundle) and you can mark the init(coder) as a convenience initializer. It seems like a little bit hacky solution and I don’t like it too much, but it does the job.
import UIKit
class ViewController: UIViewController {
init() {
super.init(nibName: nil, bundle: nil)
self.initialize()
}
required convenience init?(coder aDecoder: NSCoder) {
self.init(coder: aDecoder)
self.initialize()
}
func initialize() {
}
}
class MyFutureViewController: ViewController {
override init() {
super.init()
}
}
let vc = MyFutureViewController()UIView init
I usually create a common initializer for UIViews to make the init process more pleasant. I also set the translate autoresizing mask property to false in that initializer method, because it’s 2017 and noone uses springs & struts anymore, right?
import UIKit
class View: UIView {
init() {
super.init(frame: .zero)
self.initialize()
}
override init(frame: CGRect) {
super.init(frame: frame)
self.initialize()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.initialize()
}
func initialize() {
self.translatesAutoresizingMaskIntoConstraints = false
}
}It’s also nice to have some autolayout helpers, and if you want to initialize a view from a nib file, it’s really good to have some convenience method around.
import UIKit
extension UIView {
public convenience init(autolayout: Bool) {
self.init(frame: .zero)
self.translatesAutoresizingMaskIntoConstraints = !autolayout
}
public static func create(autolayout: Bool = true) -> Self {
let _self = self.init()
let view = _self as UIView
view.translatesAutoresizingMaskIntoConstraints = !autolayout
return _self
}
public static func createFromNib(
owner: Any? = nil,
options: [AnyHashable: Any]? = nil
) -> UIView {
return Bundle.main.loadNibNamed(
String(describing: self),
owner: owner,
options: options
)?.last as! UIView
}
}
let view = UIView(autolayout: true)Using these snippets, it’s really easy to maintain a sane init process for all the UIKit classes, because most of them ared derived from these two “primary” classes.
