The fast path to autolayout views in code

https://speakerdeck.com/banjun/auto-layout-with-an-extended-visual-format-language at AltConf19 https://speakerdeck.com/banjun/lets-start-vfl

let iconView = UIImageView() // and customize...
let nameLabel = UILabel() // and customize...

override func loadView() {
    super.loadView()
    title = "Simple Example"
    view.backgroundColor = .white
    let autolayout = northLayoutFormat(["p": 8], [
        "icon": iconView,
        "name": nameLabel])
    autolayout("H:||[icon(==64)]") // 64pt width icon on left side with default margin
    autolayout("H:||[name]||") // full width label with default margin
    autolayout("V:||-p-[icon(==64)]-p-[name]") // stack them vertically
}

See also Example project.

override init(frame: CGRect) {
    super.init(frame: frame)
    // autolayout respecting safe area without reference to container view controller
    let autolayout = northLayoutFormat([:], [
        "icon": iconView,
        "name": nameLabel])
    autolayout("H:||-(>=0)-[icon(==64)]-(>=0)-||") // 64pt fitting width icon with default margin
    autolayout("H:||[name]||") // fitting width label with default margin
    autolayout("V:||[icon(==64)]-[name]||") // stack them vertically
    // constrain iconView horizontal ambiguity to safe area center
    layoutMarginsGuide.centerXAnchor.constraint(equalTo: iconView.centerXAnchor).isActive = true
}

See also Example project.

See Example project.

Let's autolayout in code. boilerplates such as translatesAutoresizingMaskIntoConstraints = false and adding as subview are coded in northLayoutFormat().

Use Visual Format Language (VFL) for layout.

Auto Layout Guide: Visual Format Language

In addition to Apple VFL above, NorthLayout introduces || syntax for layout margin bounds.

// stick to side edges (i.e. screen edges for view of view controller)
autolayout("H:|[icon1]|")

// stick to side layout margins (avoids non safe areas)
autolayout("H:||[icon2]||")

In autolayout, there is some differences in view of view controller and independent view. northLayoutFormat is available for view controller and view. You can use | as topLayoutGuide or bottomLayoutGuide (mainly for before iOS 11) and avoid conflicting scroll adjustments on view controllers. You can also code layout simply without a view controller on views.

Available for UIView & NSView

NorthLayout 4 has supported Safe Area by translating | bounds as safe area layout guides by default.

NorthLayout 5 adds breaking changes that introduces || layout margin guides and thus | no longer respects Safe Area. Choose | to stick to edges, or || to inset in layout margins or safe area.

NorthLayout is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "NorthLayout"

Code snippets help writing VFL activated in string literal scope.

cd (NorthLayout directory)
cp CodeSnippets/*.codesnippet ~/Library/Developer/Xcode/UserData/CodeSnippets/

NorthLayout is named after where it was cocoapodized, Lake Toya in the North prefecture of Japan, the setting of Celestial Method.

NorthLayout is available under the MIT license. See the LICENSE file for more info.