Declarative layout constraints in Swift.

Blueprint started with the idea to port my Objective-C's TATLayout library to Swift. But soon it changed at all, thanks to the awesome features in the Swift language and the additions to the constraint based layout system in iOS 8.

Requirements

iOS 8.0 and Xcode 6.0 GM

Installation

Blueprint is a Cocoa Touch Framework, to use it you can:

add Blueprint.xcodeproj to your project
link Blueprint.framework
then import Blueprint

But...for now...the real thing is just one file: DeclarativeLayoutConstraint.swift so you can add the file to your project/target and that's all!

Usage

#####There are 2 formats that can be used to declare layout constraints:

view.attribute ==|<=|>= view.attribute[ *|/ multiplier][ +|- constant][ ~ priority]
view.attribute ==|<=|>= constant[ ~ priority]

Where:

view: AnyObject! (just like NSLayoutConstraint's items)

attribute: NSLayoutAttribute

extension UIView {
    left: .Left
    right: .Right
    top: .Top
    bottom: .Bottom
    leading: .Leading
    trailing: .Trailing
    width: .Width
    height: .Height
    centerX: .CenterX
    centerY: .CenterY
    baseline: .Baseline
    firstBaseline: .FirstBaseline
    leftMargin: .LeftMargin
    rightMargin: .RightMargin
    topMargin: .TopMargin
    bottomMargin: .BottomMargin
    leadingMargin: .LeadingMargin
    trailingMargin: .TrailingMargin
    centerXWithinMargins: .CenterXWithinMargins
    centerYWithinMargins: .CenterYWithinMargins
}

multiplier: CGFloat

constant: CGFloat

priority: UILayoutPriority

Example:

let topView = UIView()
topView.backgroundColor = UIColor.blueColor()
topView.setTranslatesAutoresizingMaskIntoConstraints(false)
view.addSubview(topView)
   
let bottomView = UIView()
bottomView.backgroundColor = UIColor.greenColor()
bottomView.setTranslatesAutoresizingMaskIntoConstraints(false)
view.addSubview(bottomView)
   
let label = UILabel()
label.text = "The label"
label.setTranslatesAutoresizingMaskIntoConstraints(false)
view.addSubview(label)
   
let padding: CGFloat = 20
   
NSLayoutConstraint.activateConstraints([
    label.centerX == view.centerX,
    label.centerY == view.centerY,
    topView.top == view.top + padding,
    topView.leading == view.leading + padding,
    topView.trailing == view.trailing - padding,
    topView.height >= view.height / 3,
    topView.bottom == bottomView.top + padding ~ 751,
    bottomView.height == view.height * 0.5,
    bottomView.leading == view.leading + padding,
    bottomView.trailing == view.trailing - padding,
    bottomView.bottom == view.bottom - padding
])

Unit Tests

Blueprint is driven by unit testing. Run the tests with command+U.

License

This project is under the MIT license.

cromandini/Blueprint