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 fairly rattling simple job 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: .foremost
).instantiate(
    withOwner: nil, 
    choices: nil
).first as! UIView

// does the identical as above
// let view = Bundle.foremost.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 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’ll 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 methodology is fairly easy and low cost, nevertheless there may be one little downside. You may’t get named pointers (shops) for the views, however just for the basis object. In case you are placing design components into your display, that’s high quality, but when it is advisable to show dynamic information, you may need to attain out for the underlying views as nicely. 😃

Customized views with shops & 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 manner as I informed you proper up right here. 👆 The one distinction is that you just don’t want to make use of the thing 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 comprise the whole lot you want. 🤨

// be aware: 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 traditional shops
    @IBOutlet weak var textLabel: UILabel!

    override func initialize() {
        tremendous.initialize()

        // first: load the view hierarchy to get correct shops
        let title = String(describing: sort(of: self))
        let nib = UINib(nibName: title, bundle: .foremost)
        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 crammed with correct values from the xib file. There’s one very last thing that we have to do. Even the views from the xib file are “programmatically” related to our customized view object, however visually they aren’t. 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 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’s two phrases. They’re thought-about as a foul 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’s it, now you may have a very working customized UIView object that masses a xib file so as to use it’s contents. Wasn’t so dangerous, proper? 🤪

Yet another further factor. When you don’t wish 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 aspect 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 discuss a bit of bit about IBActions. They work precisely the identical as you’d anticipate 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, you need to use the delegate sample or go together 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 will 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 don’t want a container view anymore, additionally the proprietor of the file might be ignored from the sport, it’s roughly the identical methodology as reusable cells for tables and collections created by Apple. 🍎

You must 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 making an attempt to make use of this sort of customized views from a storyboard or xib file, you gained’t be capable of use your shops, as a result of the correspondig xib of the view class gained’t be loaded. In any other case in case you are making an attempt to load it manyally you’ll run into an infinite loop and ultimately 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 operate
        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 a must to set your customized view class on the view object, as an alternative of the File’s Proprietor. You need to join your shops and mainly you’re executed with the whole lot. 🤞

Any longer you need to ALWAYS use the instantiate methodology in your customized view object. The excellent news is that the operate is generic, returns the correct occasion sort and it’s extremely reusable. Oh, btw. I already talked about the dangerous information… 🤪

There’s additionally another method by overriding awakeAfter, however I’d not depend on that answer anymore. In many of the circumstances you possibly can merely set the File’s Proprietor to your customized view, and go together with a container, that’s a protected guess. You probably have particular wants you may want the second strategy, however please watch out with that. 😉