Features

• iOS 8 compatible
• Maximum readability
• No new concepts or magic

Usage

import Pin adds new properties to Layoutable elements such as views and layout guides.

Define a constraint using operators like so:

let constraint = label.bottomPin == view.bottomPin // NSLayoutConstraint

Constants, Multipliers and Priorities

let widthConstraint = label.widthPin <= view.widthPin * 0.75 ~ UILayoutPriorityDefaultHigh
let topConstraint = label.topPin == imageView.bottomPin + 10

Convenience methods

Pin a views center. offset and multiplier is optional.

titleLabel.pinCenter(to: view) // [NSLayoutConstraint]

Pin a views edges to another view. insets is optional.

backgroundView.pinEdges(to: view) // [NSLayoutConstraint]

Pin a views edges to another views edge margins

longTextLabel.pinEdgeMargins(to: textContainer) // [NSLayoutConstraint]

Sequence of NSLayoutConstraint is extended when importing Pin with two methods.

let constraints = [
  label.centerXPin == view.centerXPin,
  label.width <= 250,
  label.topPin == view.topLayoutGuide.bottomPin
]

constraints.activate() // Activates constraints
constraints.deactivate() // Deactivates constraints

Real-world usage

You can create multiple constraints without storing them, for instance, in viewDidLoad:

override func viewDidLoad() {
	super.viewDidLoad()
	
	var constraints = [NSLayoutConstraint]()

    constraints += backgroundView.pinEdges(to: view)

    constraints += [
      titleLabel.topPin == topLayoutGuide.bottomPin + 30,

      titleLabel.centerXPin == view.centerXPin,
      titleLabel.widthPin <= view.widthPin * 0.75,

      textContainer.bottomPin == bottomLayoutGuide.topPin - 30,
      textContainer.leftPin == view.leftMarginPin,
      textContainer.rightPin == view.rightMarginPin
    ]

    constraints += longTextLabel.pinEdgeMargins(to: textContainer)

    constraints.activate()
}

You can also use NSLayoutConstraint.make for an even cleaner implementation:

NSLayoutConstraint.make { constraints in
	constraints += backgroundView.pinEdges(to: view)
	constraints.append(textLabel.width == 200)
}.activate()

Expressive syntax

If you don't fancy operators, you can use the more expressive syntax, or mix as you like:

NSLayoutConstraint.activate([
    label.topPin.equal(to: view.topMarginPin),
    label.centerXPin.equal(to: view.centerXPin),
    label.leftPin.greaterThanOrEqual(to: view.leftPin * 0.25) ~ UILayoutPriorityDefaultHigh,
    label.rightPin.lessThanOrEqual(to: view.rightPin.multiplied(by: 0.75).offset(by: 10)).prioritized(at: UILayoutPriorityDefaultHigh)
    ])

Setting up with Carthage

Carthage is a decentralized dependency manager that automates the process of adding frameworks to your Cocoa application.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Pin into your Xcode project using Carthage, add the following to your Cartfile:

github "formbound/Pin"

Credits

• David Ask (@davidask)

License

Pin is released under the MIT license. See LICENSE for details.

About Formbound

Formbound AB is a software development firm devoted to open-source development.