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Customized UIView subclass from a xib file


Loading xib information

Utilizing the contents of a xib file is a reasonably rattling straightforward activity 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: .most important).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 circumstances that is what you will want with a purpose to get your customized views. Additionally you may lengthen 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’s one little downside. You’ll be able to’t get named pointers (shops) for the views, however just for the foundation object. In case you are placing design components into your display, that is high-quality, but when it’s essential show dynamic knowledge, you would possibly need to attain out for the underlying views as properly. 😃

Customized views with shops & actions

So the right 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 informed you proper up right here. 👆 The one distinction is that you simply needn’t use the thing array returned by the strategies, however you must join your view objects by way of the interface builder, utilizing the File’s Proprietor as a reference level, plus a customized container view outlet, that’ll include every little thing you want. 🤨



class CustomView: View {

    
    @IBOutlet weak var containerView: UIView!

    
    @IBOutlet weak var textLabel: UILabel!

    override func initialize() {
        tremendous.initialize()

        
        let title = String(describing: sort(of: self))
        let nib = UINib(nibName: title, bundle: .most important)
        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 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 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 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: f*ckng UGLY! That is two phrases. They’re thought-about as a foul follow, 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 another additional factor. In the event you do not prefer to deal with views programmatically otherwise you merely do not 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 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 somewhat 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 is best to use the delegate sample or go together with a easy block. 😎

Possession and container views

It’s attainable to go away out all of the xib loading mechanism from the view occasion. We are able to 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 ignored from the sport, it is kind of the identical methodology as reusable cells for tables and collections created by Apple. 🍎

You need to know that going this manner you may’t use your default UIView init strategies programmatically anymore, as a result of the xib file will deal with 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 be capable 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 must set your customized view class on the view object, as a substitute of the File’s Proprietor. You need to join your shops and principally you are completed with every little thing. 🤞


Any more it is best to 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 is extremely reusable. Oh, btw. I already talked about the dangerous information… 🤪

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

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