call label postion and size from outside of class (Swift4) - ios

Question

What I am trying to do is assign the position and size of a label from outside a class. Then within 2 separate classes call the label to add text to it. This would save time a lot of time if this would work.
let backbutton = UILabel!
backbutton.translatesAutoresizingMaskIntoConstraints = false
backbutton.leftAnchor.constraint(equalTo: _, constant: 20).isActive = true
backbutton.topAnchor.constraint(equalTo: _, constant: 125).isActive = true
backbutton.widthAnchor.constraint(equalToConstant: 50).isActive = true
backbutton.heightAnchor.constraint(equalToConstant: 50).isActive = true
class nineViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
backbutton.text = String("red")
}
}
class two: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
backbutton.text = String("two")
}
}

Answer 1

Create a Utilities class separately to use the functions that are inside it globally.
Utilities:
class Utilities: NSObject
{
class func createLabel(on view: UIView, horizontalAnchors hAnchors: (leading: CGFloat, leadingView: UIView, trailing: CGFloat, trailingView: UIView), verticalAnchors vAnchors: (top: CGFloat, topView: UIView, bottom: CGFloat, bottomView: UIView)) -> UILabel {
let label = UILabel()
view.addSubview(label)
label.backgroundColor = UIColor.red
label.translatesAutoresizingMaskIntoConstraints = false
label.leadingAnchor.constraint(equalTo: hAnchors.leadingView.leadingAnchor, constant: hAnchors.leading).isActive = true
label.trailingAnchor.constraint(equalTo: hAnchors.trailingView.trailingAnchor, constant: -hAnchors.trailing).isActive = true
label.topAnchor.constraint(equalTo: vAnchors.topView.topAnchor, constant: vAnchors.top).isActive = true
label.bottomAnchor.constraint(equalTo: vAnchors.bottomView.topAnchor, constant: -vAnchors.bottom).isActive = true
return label
}
class func createLabel(on view: UIView, positionAnchors pAnchors: (leading: CGFloat, leadingView: UIView, top: CGFloat, topView: UIView), size: (width: CGFloat, height: CGFloat)) -> UILabel {
let label = UILabel()
view.addSubview(label)
label.backgroundColor = UIColor.red
label.translatesAutoresizingMaskIntoConstraints = false
label.leadingAnchor.constraint(equalTo: pAnchors.leadingView.leadingAnchor, constant: pAnchors.leading).isActive = true
label.topAnchor.constraint(equalTo: pAnchors.topView.topAnchor, constant: pAnchors.top).isActive = true
label.widthAnchor.constraint(equalToConstant: size.width).isActive = true
label.heightAnchor.constraint(equalToConstant: size.height).isActive = true
return label
}
}
In ViewController:
#IBOutlet weak var autoLayedoutLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
let originY: CGFloat = 50
let spacing: CGFloat = 16
let width: CGFloat = 300
let height: CGFloat = 50
let label = Utilities.createLabel(on: view, positionAnchors: (spacing, view, originY, view), size: (width, height))
label.text = "Label with Position Anchors & Size"
label.backgroundColor = UIColor.red
let label2 = Utilities.createLabel(on: view, horizontalAnchors: (spacing, view, spacing, view), verticalAnchors: (spacing + height, label, spacing, autoLayedoutLabel))
label2.text = "Label with Horizontal & Vertical Anchors"
label2.backgroundColor = UIColor.green
}

Answer 2

You can have different variable for buttonText and set his position and size in his setter like
var buttonText:String {
didSet{
backButton.text = buttonText
setFontAndPosition()
}
}
and in viewController just set the value
override func viewDidLoad() {
super.viewDidLoad()
buttonText = "red"
}

Answer 3

I found it's feasible to directly use global UILable. If you don't need to manage too many labels, this is the simplest way.
A TabBarcontroller is used for testing here.
let backbutton = UILabel()
class MyTabBarController : UITabBarController {
override func viewDidLoad() {
super.viewDidLoad()
setViewControllers([SettingViewController(), NineViewController(), TwoViewController()], animated: false)
}
}
class SettingViewController: UIViewController {
override var tabBarItem: UITabBarItem!{
get {
return UITabBarItem.init(title: "setting", image: nil, tag: 0)
}
set{
super.tabBarItem = newValue
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
self.view.addSubview(backbutton)
backbutton.text = "cool"
backbutton.translatesAutoresizingMaskIntoConstraints = false
backbutton.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: 20).isActive = true
backbutton.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 125).isActive = true
backbutton.widthAnchor.constraint(equalToConstant: 50).isActive = true
backbutton.heightAnchor.constraint(equalToConstant: 50).isActive = true
}
}
class NineViewController: UIViewController {
override var tabBarItem: UITabBarItem!{
get {
return UITabBarItem.init(title: "nine", image: nil, tag: 0)
}
set{
super.tabBarItem = newValue
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
backbutton.text = String("red")
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
backbutton.text = String("red-Appear")
}
}
class TwoViewController: UIViewController {
override var tabBarItem: UITabBarItem!{
get {
return UITabBarItem.init(title: "two", image: nil, tag: 0)
}
set{
super.tabBarItem = newValue
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
backbutton.text = String("two")
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
backbutton.text = String("two-Appear")
}
}
If you prefer defining the label inside one class. You may define the global UILabel as this:
weak var backbutton: UILabel!
class SettingViewController: UIViewController {
let mybutton = UILabel()
backbutton = mybutton
// continue
}
You don't need to change any other codes.
Now is the second part of the story. If you wanna setup a global UILabel outside any view, is that possible. Without constraints it's very simple like this:
let backbutton: UILabel! = {
let button = UILabel()
button.text = "test"
button.frame = CGRect.init(x: 200, y: 200, width: 50, height: 50)
return button
}()
The setting View changes like this :
class SettingViewController: UIViewController {
override var tabBarItem: UITabBarItem!{
get {
return UITabBarItem.init(title: "setting", image: nil, tag: 0)
}
set{
super.tabBarItem = newValue
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
self.view.addSubview(backbutton)
}
}
It's clear there is only one line in the SettingVC. But if you need to use constraints, what should we do? Everything else is fine, but the position of UILabel constraints depends on the superView of UILabel. So an extension can be used here to make things easier.
let specialLabelTag = 1001
let backbutton: UILabel! = {
let button = UILabel()
button.tag = specialLabelTag
button.text = "test" // for test purpose
button.translatesAutoresizingMaskIntoConstraints = false
button.widthAnchor.constraint(equalToConstant: 50).isActive = true
button.heightAnchor.constraint(equalToConstant: 50).isActive = true
return button
}()
extension UILabel{
override open func didMoveToSuperview() {
superview?.didMoveToSuperview()
if(tag == specialLabelTag){
leftAnchor.constraint(equalTo: superview!.leftAnchor, constant: 20).isActive = true
topAnchor.constraint(equalTo: superview!.topAnchor, constant: 125).isActive = true
}
}
The tag used in extension is to identify the global UILabel in order not to affect other UILabels. Only position constraints are needed in the extension. SettingUP vc is as same as before.
Now you can build a label without any view class. But you have to add them somewhere and modify the text as you like. Hope this is the answer to the question.
BTW, you can subclass the UILabel to MyUILabel with above code and then make it global (just put outside any class). It would be much easier because you don't need to use specialLabelTag.
let backbutton = MyUILabel()