Customized UIView subclass from a xib file

Loading xib information

Utilizing the contents of a xib file is a fairly rattling simple process to do. You need to use the next two strategies to load the contents (aka. the view hierarchy) of the file.

let view = UINib(nibName: "CustomView", bundle: .fundamental).instantiate(withOwner: nil, choices: nil).first as! UIView

view.body = self.view.bounds
self.view.addSubview(view)

The snippet above will merely instantiate a view object from the xib file. You’ll be able to have a number of root objects within the view hierarchy, however this time let’s simply choose the primary one and use that. I assume that in 99% of the instances that is what you will want to be able to get your customized views. Additionally you’ll be able to prolong the UIView object with any of the options above to create a generic view loader. Extra on that later… 😊

This technique is fairly easy and low cost, nonetheless there may be one little downside. You’ll be able to’t get named pointers (shops) for the views, however just for the basis object. If you’re placing design parts into your display screen, that is advantageous, but when it’s worthwhile to show dynamic knowledge, you may need to attain out for the underlying views as properly. 😃

Customized views with shops & actions

So the correct technique to load customized views from xib information goes one thing like this:

Inside your customized view object, you instantiate the xib file precisely the identical approach as I advised you proper up right here. 👆 The one distinction is that you just need not use the item array returned by the strategies, however you need to join your view objects by the interface builder, utilizing the File’s Proprietor as a reference level, plus a customized container view outlet, that’ll include all the things you want. 🤨

class CustomView: View {

    
    @IBOutlet weak var containerView: UIView!

    
    @IBOutlet weak var textLabel: UILabel!

    override func initialize() {
        tremendous.initialize()

        
        let identify = String(describing: kind(of: self))
        let nib = UINib(nibName: identify, bundle: .fundamental)
        nib.instantiate(withOwner: self, choices: nil)

        
        self.addSubview(self.containerView)
        self.containerView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            self.containerView.topAnchor.constraint(equalTo: self.topAnchor),
            self.containerView.bottomAnchor.constraint(equalTo: self.bottomAnchor),
            self.containerView.leadingAnchor.constraint(equalTo: self.leadingAnchor),
            self.containerView.trailingAnchor.constraint(equalTo: self.trailingAnchor),
        ])
    }
}

So the initialize technique right here is simply loading the nib file with the proprietor of self. After the loading course of completed, your outlet pointers are going to be stuffed with correct values from the xib file. There may be one final thing that we have to do. Even the views from the xib file are “programmatically” linked to our customized view object, however visually they are not. So we’ve got so as to add our container view into the view hierarchy. 🤐

If you wish to use your customized view object, you simply should create a brand new occasion from it – inside a view controller – and eventually be happy so as to add it as a subview!

One phrase about bounds, frames aka. springs and struts: f*ckng UGLY! That is two phrases. They’re thought of as a nasty apply, so please use auto format, I’ve a pleasant tutorial about anchors, they’re wonderful and studying them takes about quarter-hour. 😅

class ViewController: UIViewController {

    weak var customView: CustomView!

    override func loadView() {
        tremendous.loadView()

        let customView = CustomView()
        self.view.addSubview(customView)
        NSLayoutConstraint.activate([
            customView.topAnchor.constraint(equalTo: self.view.topAnchor),
            customView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor),
            customView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            customView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
        ])
        self.customView = customView
    }

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.customView.textLabel.textual content = "Lorem ipsum"
    }
}

That is it, now you might have a totally working customized UIView object that hundreds a xib file to be able to use it is contents. Wasn’t so unhealthy, proper? 🤪

Yet another additional factor. For those who do not wish to deal with views programmatically otherwise you merely do not need to fiddle with the loadView technique, simply take away it fully. Subsequent put the @IBOutlet key phrase proper earlier than your customized view class variable. Open your storyboard utilizing IB, then drag & drop a brand new UIView factor to your controller and join the customized view outlet. It ought to work like magic. 💫

I promised shops and actions within the heading of this part, so let’s speak just a little bit about IBActions. They work precisely the identical as you’d anticipate them with controllers. You’ll be able to merely hook-up a button to your customized view and delegate the motion to the customized view class. If you wish to ahead touches or particular actions to a controller, it’s best to use the delegate sample or go along with a easy block. 😎

Possession and container views

It’s attainable to depart out all of the xib loading mechanism from the view occasion. We are able to create a set of extensions to be able to have a pleasant view loader with a customized view class from a xib file. This manner you do not want a container view anymore, additionally the proprietor of the file may be omitted from the sport, it is kind of the identical technique as reusable cells for tables and collections created by Apple. 🍎

It is best to know that going this manner you’ll be able to’t use your default UIView init strategies programmatically anymore, as a result of the xib file will care for the init course of. Additionally in case you are attempting to make use of this sort of customized views from a storyboard or xib file, you will not have the ability to use your shops, as a result of the correspondig xib of the view class will not be loaded. In any other case in case you are attempting to load it manyally you will run into an infinite loop and finally your app will crash like hell. 😈

import UIKit

extension UINib {
    func instantiate() -> Any? {
        return self.instantiate(withOwner: nil, choices: nil).first
    }
}

extension UIView {

    static var nib: UINib {
        return UINib(nibName: String(describing: self), bundle: nil)
    }

    static func instantiate(autolayout: Bool = true) -> Self {
        
        func instantiateUsingNib<T: UIView>(autolayout: Bool) -> T {
            let view = self.nib.instantiate() as! T
            view.translatesAutoresizingMaskIntoConstraints = !autolayout
            return view
        }
        return instantiateUsingNib(autolayout: autolayout)
    }
}

class CustomView: UIView {

    @IBOutlet weak var textLabel: UILabel!
}

Similar to with desk or assortment view cells this time you need to set your customized view class on the view object, as an alternative of the File’s Proprietor. It’s important to join your shops and principally you are accomplished with all the things. 🤞

Any more it’s best to ALWAYS use the instantiate technique in your customized view object. The excellent news is that the perform is generic, returns the correct occasion kind and it is extremely reusable. Oh, btw. I already talked about the unhealthy information… 🤪

There may be additionally yet one more method by overriding awakeAfter, however I might not depend on that resolution anymore. In many of the instances you’ll be able to merely set the File’s Proprietor to your customized view, and go along with a container, that is a secure guess. When you have particular wants you may want the second method, however please watch out with that. 😉