Customized UIView subclass from a xib file

I have already got a complete information about initializing views and controllers, however that one lacks a really particular case: making a customized view utilizing interface builder. 🤷‍♂️

Loading xib recordsdata

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

let view = UINib(
    nibName: "CustomView", 
    bundle: .major
).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 may have a number of root objects within the view hierarchy, however this time let’s simply decide the primary one and use that. I assume that in 99% of the circumstances that is what you may want so as to get your customized views. Additionally you possibly can 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 may’t get named pointers (retailers) for the views, however just for the basis object. In case you are placing design components into your display screen, that is fantastic, but when it is advisable to show dynamic information, you may need to attain out for the underlying views as effectively. 😃

Customized views with retailers & actions

So the correct solution to load customized views from xib recordsdata goes one thing like this:

Inside your customized view object, you instantiate the xib file precisely the identical manner as I instructed you proper up right here. 👆 The one distinction is that you simply need not use the article array returned by the strategies, however you must join your view objects via the interface builder, utilizing the File’s Proprietor as a reference level, plus a customized container view outlet, that’ll comprise the whole lot you want. 🤨

class CustomView: View {

    
    @IBOutlet weak var containerView: UIView!

    
    @IBOutlet weak var textLabel: UILabel!

    override func initialize() {
        tremendous.initialize()

        
        let title = String(describing: kind(of: self))
        let nib = UINib(nibName: title, bundle: .major)
        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 full of correct values from the xib file. There’s one last item that we have to do. Even the views from the xib file are “programmatically” linked to our customized view object, however visually they don’t seem to be. So we now have 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 at liberty so as to add it as a subview!

One phrase about bounds, frames aka. springs and struts: fucking UGLY! That is two phrases. They’re thought-about as a nasty observe, so please use auto structure, 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 could have a totally working customized UIView object that hundreds a xib file so as to use it is contents. Wasn’t so unhealthy, proper? 🤪

Yet one more additional factor. For those who do not prefer to deal with views programmatically otherwise you merely do not need to fiddle with the loadView technique, simply take away it completely. 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 aspect to your controller and join the customized view outlet. It ought to work like magic. 💫

I promised retailers and actions within the heading of this part, so let’s speak slightly bit about IBActions. They work precisely the identical as you’d count on them with controllers. You may 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 is best to use the delegate sample or go along with a easy block. 😎

Possession and container views

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

It is best to know that going this fashion you possibly can’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 making an attempt to make use of this sort of customized views from a storyboard or xib file, you will not have the ability to use your retailers, as a result of the correspondig xib of the view class will not be loaded. In any other case in case you are making an attempt to load it manyally you may 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 must set your customized view class on the view object, as a substitute of the File’s Proprietor. It’s important to join your retailers and principally you are finished with the whole lot. 🤞

To any extent further it is 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’s additionally another approach by overriding awakeAfter, however I’d not depend on that resolution anymore. In many of the circumstances you possibly can merely set the File’s Proprietor to your customized view, and go along with a container, that is a secure wager. In case you have particular wants you may want the second method, however please watch out with that. 😉