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 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 decide the primary one and use that. I assume that in 99% of the instances that is what you will want with a purpose 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’s one little disadvantage. You’ll be able to’t get named pointers (retailers) for the views, however just for the basis object. If you’re placing design components into your display screen, that is nice, but when it is advisable to show dynamic information, you may wish to attain out for the underlying views as properly. 😃

Customized views with retailers & actions

So the correct option 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 means as I advised you proper up right here. 👆 The one distinction is that you simply need not use the item array returned by the strategies, however it’s a must 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 pieces 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 don’t seem to be. So we’ve so as to add our container view into the view hierarchy. 🤐

If you wish to use your customized view object, you simply must create a brand new occasion from it – inside a view controller – and at last be happy 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 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 could have a very working customized UIView object that hundreds a xib file with a purpose to use it is contents. Wasn’t so dangerous, proper? 🤪

Yet one more further factor. In the event you do not prefer to deal with views programmatically otherwise you merely do not wish 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 ingredient 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 a little bit 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, you must use the delegate sample or go together with a easy block. 😎

Possession and container views

It’s potential to depart out all of the xib loading mechanism from the view occasion. We will create a set of extensions with a purpose 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 will be overlooked 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 fashion 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 if you’re making an attempt to make use of this type 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 if you’re making an attempt 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 it’s a must to set your customized view class on the view object, as a substitute of the File’s Proprietor. You must join your retailers and mainly you are finished with all the pieces. 🤞

Any further you must ALWAYS use the instantiate technique in your customized view object. The excellent news is that the operate is generic, returns the correct occasion kind and it is extremely reusable. Oh, btw. I already talked about the dangerous information… 🤪

There may be additionally another approach by overriding awakeAfter, however I might not depend on that resolution anymore. In a lot of the instances you’ll be able to merely set the File’s Proprietor to your customized view, and go together with a container, that is a protected wager. If in case you have particular wants you may want the second method, however please watch out with that. 😉