Tiny Swift DSL for Autolayout
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Framework Support Swift Package Manager Jan 9, 2016
Sources Convert to Swift 3 Nov 25, 2016
SwiftAutoLayout.xcodeproj Add SWIFT_VERSION to all targets Dec 29, 2016
SwiftAutoLayoutTests Convert to Swift 3 Nov 25, 2016
.gitignore Support Swift Package Manager Jan 9, 2016
LICENSE Add LICENSE Jun 18, 2014
Package.swift Support Swift Package Manager Jan 9, 2016
README.md Support Swift Package Manager Jan 9, 2016



SwiftAutoLayout is a tiny DSL for Autolayout intended to provide a more declarative way to express layout constraints. Here's a quick example:

// this:
let constraint = view1.left == view2.right * 2.0 + 10.0 ~ 750
// is equivalent to:
let constraint = NSLayoutConstraint(item: view1, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: view2, attribute: NSLayoutAttribute.Right, multiplier: 2.0, constant: 10.0)
constraint.priority = 750

You may notice that this looks a lot like the linear equation that a constraint represents. From the Apple documentation:

The relationship involves a first attribute, a relationship type, and a modified second value formed by multiplying an attribute by a constant factor and then adding another constant factor to it. In other words, constraints look very much like linear equations of the following form:

attribute1 == multiplier × attribute2 + constant

SwiftAutoLayout allows you to more effectively communicate the intent of a constraint by making the syntax more similar to the equation that it represents.


Use Swift Package Manager or add SwiftAutoLayout.xcodeproj as a subproject and link against either SwiftAutoLayout-iOS.framework or SwiftAutoLayout-Mac.framework depending on the platform.


Layout attributes are defined as properties added in extensions of UIView and UILayoutGuide on iOS and NSView and NSLayoutGuide on OS X. For example, UIView.width and UIView.height represent NSLayoutAttribute.Width and NSLayoutAttribute.Height, respectively.

Layout guides (conforming to UILayoutSupport) in UIViewController are also supported using the topLayoutGuideTop, topLayoutGuideBottom, bottomLayoutGuideTop, and bottomLayoutGuideBottom properties.


Relations are expressed using the overloaded operators == (NSLayoutRelation.Equal), >= (NSLayoutRelation.GreaterThanOrEqual), and <= (NSLayoutRelation.LessThanOrEqual).


Activating Single Constraint

(view1.left == view2.right * 2.0 + 10.0 ~ 750).active = true

Activating Multiple Constraints

    view2.centerX == view2.superview!.centerX,
    view2.centerY == view2.superview!.centerY,
    view1.left == view2.right * 2.0 + 10.0 ~ 750,
    view1.top == view2.bottom + 5.0,
    view1.width >= 200,
    view1.height >= 400,
    view1.trailing == layoutGuide.trailing,
    view2.leading == layoutGuide.leading



SwiftAutoLayout is licensed under the MIT License.