Load view from XIB as a subview of a scrollview - ios

Question

I'm still a SO and Swift newbie, so please, be patient and feel free to skip this question :-)
In the body of a XIB's awakeFromNib, I want to load some views as subviews of a UIScrollView (basically, the XIB contains a scrollview, a label and a button).
The scrollview perfectly works if in a loop I load views I create on the fly, eg.
let customView = UIView(frame: CGRect(x: 0, y: 0, width: 300, height: 150))
customView.frame = CGRect(x: i*300 , y: 0, width: 300, height: 150)
customView.translatesAutoresizingMaskIntoConstraints = false
scrollView.addSubview(customView)
But I have a different goal.
In another XIB I have an image view and a stackview with some labels. This XIB is connected in the storyboard to a class SingleEvent that extends UIView.
I want to do the following:
use the XIB as a sort of "blueprint" and load the same view multiple times in my scrollview;
pass to any instance some data;
Is this possible?
I tried to load the content of the XIB this way:
let customView = Bundle.main.loadNibNamed("SingleEvent", owner: self, options: nil)?.first as? SingleEvent
and this way:
let customView = SingleEvent()
The first one makes the app crash, while the second causes no issue, but I can't see any effect (it doesn't load anything).
The content of my latest SingleEvent is the following:
import UIKit
class SingleEvent: UIView {
#IBOutlet weak var label:UILabel!
#IBOutlet weak var imageView:UIImageView!
override init(frame: CGRect) {
super.init(frame: frame)
loadViewFromNib()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
loadViewFromNib()
}
func loadViewFromNib() -> UIView {
let myView = Bundle.main.loadNibNamed("SingleEvent", owner: self, options: nil)?.first as! UIView
return myView
}
}
Thanks in advance, any help is appreciated :-)

Answer 1

There are a number of approaches to loading custom views (classes) from xibs. You may find this method a bit easier.
First, create your xib like this:
Note that the Class of File's Owner is the default (NSObject).
Instead, assign your custom class to the "root" view in your xib:
Now, our entire custom view class looks like this:
class SingleEvent: UIView {
#IBOutlet var topLabel: UILabel!
#IBOutlet var middleLabel: UILabel!
#IBOutlet var bottomLabel: UILabel!
#IBOutlet var imageView: UIImageView!
}
And, instead of putting loadNibNamed(...) inside our custom class, we create a UIView extension:
extension UIView {
class func fromNib<T: UIView>() -> T {
return Bundle.main.loadNibNamed(String(describing: T.self), owner: nil, options: nil)![0] as! T
}
}
To load and use our custom class, we can do this:
class FromXIBViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// create an instance of SingleEvent from its xib/nib
let v = UIView.fromNib() as SingleEvent
// we're going to use auto-layout & constraints
v.translatesAutoresizingMaskIntoConstraints = false
// set the text of the labels
v.topLabel?.text = "Top Label"
v.middleLabel?.text = "Middle Label"
v.bottomLabel?.text = "Bottom Label"
// set the image
v.imageView.image = UIImage(named: "myImage")
// add the SingleEvent view
view.addSubview(v)
// constrain it 200 x 200, centered X & Y
NSLayoutConstraint.activate([
v.widthAnchor.constraint(equalToConstant: 200.0),
v.heightAnchor.constraint(equalToConstant: 200.0),
v.centerXAnchor.constraint(equalTo: view.centerXAnchor),
v.centerYAnchor.constraint(equalTo: view.centerYAnchor),
])
}
}
With a result of:
And... here is an example of loading 10 instances of SingleEvent view and adding them to a vertical scroll view:
class FromXIBViewController: UIViewController {
var theScrollView: UIScrollView = {
let v = UIScrollView()
v.translatesAutoresizingMaskIntoConstraints = false
v.backgroundColor = .cyan
return v
}()
var theStackView: UIStackView = {
let v = UIStackView()
v.translatesAutoresizingMaskIntoConstraints = false
v.axis = .vertical
v.alignment = .fill
v.distribution = .fill
v.spacing = 20.0
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
// add the scroll view to the view
view.addSubview(theScrollView)
// constrain it 40-pts on each side
NSLayoutConstraint.activate([
theScrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 40.0),
theScrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -40.0),
theScrollView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40.0),
theScrollView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40.0),
])
// add a stack view to the scroll view
theScrollView.addSubview(theStackView)
// constrain it 20-pts on each side
NSLayoutConstraint.activate([
theStackView.topAnchor.constraint(equalTo: theScrollView.topAnchor, constant: 20.0),
theStackView.bottomAnchor.constraint(equalTo: theScrollView.bottomAnchor, constant: -20.0),
theStackView.leadingAnchor.constraint(equalTo: theScrollView.leadingAnchor, constant: 20.0),
theStackView.trailingAnchor.constraint(equalTo: theScrollView.trailingAnchor, constant: -20.0),
// stackView width = scrollView width -40 (20-pts padding on left & right
theStackView.widthAnchor.constraint(equalTo: theScrollView.widthAnchor, constant: -40.0),
])
for i in 0..<10 {
// create an instance of SingleEvent from its xib/nib
let v = UIView.fromNib() as SingleEvent
// we're going to use auto-layout & constraints
v.translatesAutoresizingMaskIntoConstraints = false
// set the text of the labels
v.topLabel?.text = "Top Label: \(i)"
v.middleLabel?.text = "Middle Label: \(i)"
v.bottomLabel?.text = "Bottom Label: \(i)"
// set the image (assuming we have images named myImage0 thru myImage9
v.imageView.image = UIImage(named: "myImage\(i)")
theStackView.addArrangedSubview(v)
}
}
}
Result:

Answer 2

Ok, I see. The problem probably in fact that loadViewFromNib function return UIView from xib, but you doesn't use it any way.
Let's try this way:
1) Make your loadViewFromNib function static
// Return our SingleEvent instance here
static func loadViewFromNib() -> SingleEvent {
let myView = Bundle.main.loadNibNamed("SingleEvent", owner: self, options: nil)?.first as! SingleEvent
return myView
}
2) Remove all inits in SingleEvent class
3) Init it in needed place like this:
let customView = SingleView.loadViewFromNib()
To pass data inside view you can create new function in SingleView class:
func configureView(with dataModel:DataModel) {
//Set data to IBOutlets here
}
And use it from outside like this:
let customView = SingleView.loadViewFromNib()
let dataModel = DataModel()
customView.configureView(with: dataModel)