How to set the frame of a ViewController without storyboard - ios

Question

I want to create a view (e.g. 100x100) with ViewController without using the storyboard. I am wondering what the best way to declare the frame of the ViewController is.
I tried:
class MyLittleViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
}
}
And I tried to see this view on my MainViewController:
override func viewDidLoad() {
super.viewDidLoad()
let myLittleView = MyLittleViewController()
myLittleView.willMove(toParent: self)
myLittleView.view.translatesAutoresizingMaskIntoConstraints = false
myLittleView.view.backgroundColor = .red
view.addSubview(myLittleView.view)
// enable auto-sizing (for example, if the device is rotated)
myLittleView.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
self.addChild(myLittleView)
myLittleView.didMove(toParent: self)
myLittleView.view.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
myLittleView.view.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
}
It doesn't work like I expected because the little view doesn't appear on the main view. Any hints?

Answer 1

You shouldn't mix frame layout with auto-layout set a width & height constraints also
NSLayoutConstraint.activate([
myLittleView.view.centerXAnchor.constraint(equalTo: view.centerXAnchor),
myLittleView.view.centerYAnchor.constraint(equalTo: view.centerYAnchor),
myLittleView.view.heightAnchor.constraint(equalToConstant:100),
myLittleView.view.widthAnchor.constraint(equalToConstant:100)
])
OR
myLittleView.view.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
myLittleView.view.center = view.center
OR
override func loadView() {
view = UIView()
view.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
}
Edit:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .green
let myLittleView = MyLittleViewController()
myLittleView.willMove(toParent: self)
myLittleView.view.backgroundColor = .red
view.addSubview(myLittleView.view)
// enable auto-sizing (for example, if the device is rotated)
myLittleView.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
self.addChild(myLittleView)
myLittleView.didMove(toParent: self)
myLittleView.view.center = view.center
}
}
class MyLittleViewController: UIViewController {
override func loadView() {
view = UIView()
view.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
}
}

Answer 2

Another way to set frame of the view controller is override method loadView() and set the view frame like this
func loadView() {
view = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
}