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 information

Utilizing the contents of a xib file is a fairly rattling straightforward process to do. You should utilize 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

// does the identical as above
// let view = Bundle.fundamental.loadNibNamed(
//    "CustomView", 
//    proprietor: 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 possibly can 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’ll want with a view 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 methodology is fairly easy and low-cost, nonetheless there may be one little disadvantage. You possibly can’t get named pointers (retailers) for the views, however just for the foundation object. If you’re placing design components into your display screen, that’s high-quality, but when you should show dynamic knowledge, you would possibly need to attain out for the underlying views as nicely. 😃

Customized views with retailers & actions

So the right approach 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 informed you proper up right here. 👆 The one distinction is that you simply don’t want to make use of the item array returned by the strategies, however it’s important 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 the whole lot you want. 🤨

// word: view object is from my earlier tutorial, with autoresizing masks disabled
class CustomView: View {

    // that is going to be our container object
    @IBOutlet weak var containerView: UIView!

    // different ordinary retailers
    @IBOutlet weak var textLabel: UILabel!

    override func initialize() {
        tremendous.initialize()

        // first: load the view hierarchy to get correct retailers
        let identify = String(describing: sort(of: self))
        let nib = UINib(nibName: identify, bundle: .fundamental)
        nib.instantiate(withOwner: self, choices: nil)

        // subsequent: append the container to our view
        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 methodology 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’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 aren’t. So we have now 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’s two phrases. They’re thought-about as a nasty apply, so please use auto structure, I’ve a pleasant tutorial about anchors, they’re superb 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’s it, now you will have a very working customized UIView object that hundreds a xib file with a view to use it’s contents. Wasn’t so unhealthy, proper? 🤪

Another additional factor. When you don’t prefer to deal with views programmatically otherwise you merely don’t need to fiddle with the loadView methodology, 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 somewhat bit about IBActions. They work precisely the identical as you’d anticipate them with controllers. You possibly can 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 doable to depart out all of the xib loading mechanism from the view occasion. We are able to create a set of extensions with a view to have a pleasant view loader with a customized view class from a xib file. This fashion you don’t want a container view anymore, additionally the proprietor of the file will be ignored from the sport, it’s roughly the identical methodology as reusable cells for tables and collections created by Apple. 🍎

You need 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 handle the init course of. Additionally in case you are attempting to make use of this type of customized views from a storyboard or xib file, you received’t be capable of use your retailers, as a result of the correspondig xib of the view class received’t be loaded. In any other case in case you are attempting to load it manyally you’ll 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 {
        // generic helper perform
        func instantiateUsingNib(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!
}

// utilization (inside a view controller for instance)
// let view = CustomView.instantiate()

Similar to with desk or assortment view cells this time it’s important to set your customized view class on the view object, as a substitute of the File’s Proprietor. You need to join your retailers and principally you’re achieved with the whole lot. 🤞

Any more you must ALWAYS use the instantiate methodology in your customized view object. The excellent news is that the perform is generic, returns the right occasion sort and it’s extremely reusable. Oh, btw. I already talked about the unhealthy information… 🤪

There’s additionally yet one more method by overriding awakeAfter, however I might not depend on that answer anymore. In many of the instances you possibly can merely set the File’s Proprietor to your customized view, and go together with a container, that’s a protected wager. When you’ve got particular wants you would possibly want the second method, however please watch out with that. 😉