iOS Auto Format tutorial programmatically

Rotation assist

In case your software goes to assist a number of gadget orientations, you must implement the next strategies inside your view controller.

class ViewController: UIViewController {

    override var shouldAutorotate: Bool {
        return false
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .portrait
    }

    override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
        return .portrait
    }
}

Clearly you’ll be able to change the return values to assist not simply portrait, however panorama mode as properly. That is fairly straightforward, nonetheless in case your controller is embedded inside a navigation or a tab bar controller the rotation stops working. On this case, it’s a must to subclass the UINavigationController, and it’s a must to return the proper values from the highest view controller.

class NavigationController: UINavigationController {

    override var shouldAutorotate: Bool {
        if let shouldRotate = self.topViewController?.shouldAutorotate {
            return shouldRotate
        }
        return tremendous.shouldAutorotate
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        if let orientation = self.topViewController?.supportedInterfaceOrientations {
            return orientation
        }
        return tremendous.supportedInterfaceOrientations
    }

    override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
        if let orientation = self.topViewController?.preferredInterfaceOrientationForPresentation {
            return orientation
        }
        return tremendous.preferredInterfaceOrientationForPresentation
    }
}

The identical logic applies when you have a UITabBarController, however as an alternative of the highest view controller, it’s a must to use the selectedIndex, and return the properties primarily based on the chosen view controller.

class TabBarController: UITabBarController {

    override var shouldAutorotate: Bool {
        if let viewController = self.viewControllers?[self.selectedIndex] {
            return viewController.shouldAutorotate
        }
        return tremendous.shouldAutorotate
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        if let viewController = self.viewControllers?[self.selectedIndex] {
            return viewController.supportedInterfaceOrientations
        }
        return tremendous.supportedInterfaceOrientations
    }

    override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
        if let viewController = self.viewControllers?[self.selectedIndex] {
            return viewController.preferredInterfaceOrientationForPresentation
        }
        return tremendous.preferredInterfaceOrientationForPresentation
    }
}

This fashion your embedded controller can management the supported orientations. Oh, by the way in which you should use this technique to cahnge the standing bar model.

Constraints

With a view to perceive constraints and the present state of the Auto Format engine, we should always return to in time and begin the story from the start.

Springs and struts

Keep in mind the primary iPhone? One display to rule all of them! 320×480, no constraints, no adaptivity, simply frames and bounds. Positioning views on a set dimension canvas is completely a no brainer, right here is an instance.

class ViewController: UIViewController {

    weak var sq.: UIView!

    var squareFrame: CGRect {
        let midX = self.view.bounds.midX
        let midY = self.view.bounds.midY
        let dimension: CGFloat = 64
        return CGRect(x: midX-size/2, y: midY-size/2, width: dimension, peak: dimension)
    }

    override func loadView() {
        tremendous.loadView()

        let sq. = UIView()
        self.view.addSubview(sq.)
        self.sq. = sq.
    }

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.sq..backgroundColor = .yellow
    }

    override func viewDidLayoutSubviews() {
        tremendous.viewDidLayoutSubviews()

        self.sq..body = self.squareFrame
    }
}

With the viewDidLayoutSubviews technique it is tremendous handy to assist rotation, I simply must re-calculate the body of the view each time if the bounding rectangle adjustments. You may assume hey, that is straightforward, however what occurs if it’s a must to assist a lot of gadget sizes?

Do the maths!

For one single object it is really easy to make the calculations, however normally you have got multiple view on display. These views can have relations to one another, and a simple arithmetic trick can lead you to an entire chaos of body calculations, do you even like arithmetic? There have to be a greater means!

Auto Format

With iOS6 Apple introduced us the holy grail of format applied sciences. It was the proper successor of the earlier system. Everybody adopted it quick, that is why Apple engineers utterly eliminated body primarily based format APIs within the subsequent launch… #justkidding

Other than the joke, it was the start of a brand new period, increasingly more units had been born, and with Auto Format constraints it was tremendous straightforward to keep up views. Now we should always refactor the earlier instance with format constraints.

class ViewController: UIViewController {

    weak var sq.: UIView!

    override func loadView() {
        tremendous.loadView()

        let sq. = UIView()
        self.view.addSubview(sq.)
        sq..translatesAutoresizingMaskIntoConstraints = false
        self.view.addConstraints([
            NSLayoutConstraint(item: square, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .width, multiplier: 1.0, constant: 64),
            NSLayoutConstraint(item: square, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .height, multiplier: 1.0, constant: 64),
            NSLayoutConstraint(item: square, attribute: .centerX, relatedBy: .equal, toItem: self.view, attribute: .centerX, multiplier: 1.0, constant: 0),
            NSLayoutConstraint(item: square, attribute: .centerY, relatedBy: .equal, toItem: self.view, attribute: .centerY, multiplier: 1.0, constant: 0),
        ])
        self.sq. = sq.
    }

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.sq..backgroundColor = .yellow
    }
}

As you’ll be able to see we need not manually calculate the body of the view, nonetheless creating constraints programmatically will not be so handy. That is why Apple made the constraint Visible Format Language.

VFL = WTF?

Truly this VFL is so dangerous that I do not even need to demo it, however anyway…

class ViewController: UIViewController {

    weak var sq.: UIView!

    override func loadView() {
        tremendous.loadView()

        let sq. = UIView()
        self.view.addSubview(sq.)
        sq..translatesAutoresizingMaskIntoConstraints = false

        let views: [String:Any] = ["view": self.view, "subview": square]
        let vertical = NSLayoutConstraint.constraints(withVisualFormat: "V:[view]-(<=1)-[subview(==64)]", choices: .alignAllCenterX, metrics: nil, views: views)

        let horizontal = NSLayoutConstraint.constraints(withVisualFormat: "H:[view]-(<=1)-[subview(==64)]", choices: .alignAllCenterY, metrics: nil, views: views)
        self.view.addConstraints(vertical)
        self.view.addConstraints(horizontal)
        self.sq. = sq.
    }

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.sq..backgroundColor = .yellow
    }
}

God forbid the engineer who invented this black magic. 🙂

In order you’ll be able to see we positively have an issue with constraints. Creating all of your constraints sucks, no less than it should price many many traces of code. After all you should use the magical interface builder, however the place’s the enjoyable should you simply drag traces?

Creating constraints programmatically isn’t any higher than calculating frames, it is going to lead you to the identical stage of complexity and even worse, this is the reason so many third social gathering frameworks got here alive and finally Apple issued the issue as properly.

I’ve a tremendous article about mastering Auto Format anchors, I extremely suggest studying it if you wish to get conversant in anchors. 📖

Anchors

Anchors had been born as a result of Auto Format had some development flaws.

The NSLayoutAnchor class is a manufacturing unit class for creating NSLayoutConstraint objects utilizing a fluent API. Use these constraints to programatically outline your format utilizing Auto Format.

class ViewController: UIViewController {

    weak var sq.: UIView!

    override func loadView() {
        tremendous.loadView()

        let sq. = UIView()
        self.view.addSubview(sq.)
        sq..translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            square.widthAnchor.constraint(equalToConstant: 64),
            square.heightAnchor.constraint(equalToConstant: 64),
            square.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
            square.centerYAnchor.constraint(equalTo: self.view.centerYAnchor),
        ])
        self.sq. = sq.
    }

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.sq..backgroundColor = .yellow
    }
}

See, completely rocks! Anchors are one of the best ways of utilizing for Auto Format constraints.

Adaptive format

When you take a look at the present state of built-in apps offered by Apple, you’ll be able to see that solely a few of them are responsive / adaptive. Basically, apps that utilizing assortment views are easier to adapt for greater screens, or totally different gadget orientations.

ALWAYS use assortment views

Besides if it is only one view on the middle of the display, you must construct up your person interfaces utilizing assortment views. It will provide you with reusability, decrease reminiscence overhead, scrolling and plenty of extra advantages. You do not even must calculate the silly index pahts in case you are utilizing my CollectionView micro framework.

Auto Format with layers

Auto Format is nice, however typically it’s a must to work with layers instantly. Now on this scenario, you continue to must do some calculations. You may simply override the bounds property and replace frames within the didSet block in case you are coping with a view subclass.

override var bounds: CGRect {
    didSet {
        self.gradientLayer.body = self.bounds
    }
}

An alternative choice is to override the viewDidLayoutSubviews technique contained in the view controller, and set the body of the layer primarily based on the brand new bounds.

override func viewDidLayoutSubviews() {
    tremendous.viewDidLayoutSubviews()

    self.gradientView.gradientLayer.body = self.gradientView.bounds
}

You can too use plain previous Key-Worth Observing to watch an objet’s bounds property and replace the body of the layer in line with that.

self.addObserver(self, forKeyPath: "bounds", choices: .new, context: nil)

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard keyPath == "bounds" else {
        return tremendous.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
    }
    self.gradientLayer.body = self.bounds
}

deinit {
    self.removeObserver(self, forKeyPath: "bounds")
}

Animating nook radius

To start with if you wish to animate a view whereas utilizing constraint primarily based layouts, it’s a must to do one thing like this.

self.widthConstraint.fixed = 64
UIView.animate(withDuration: 0.5, animations: {
    self.view.layoutIfNeeded()
}, completion: nil)

Now if you wish to animate the nook radius of a view, you’ll be able to all the time use the normal means, and set the cornerRadius property of the layer on a bounds change.

However, we have this fancy new UIViewPropertyAnimator API since iOS 10.

self.imageView.layer.cornerRadius = 16
UIViewPropertyAnimator(length: 2.5, curve: .easeInOut) {
    self.imageView.layer.cornerRadius = 32
}.startAnimation()

It is fairly easy, you’ll be able to even apply a cornerMask to spherical simply a few of the corners. The layer primarily based format examples are contained in the offered supply code for the article alongside with an entire pattern for every Auto Format method. You may obtain or clone it from the The.Swift.Dev tutorials repository.