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-Mac.framework depending on the platform.
Layout attributes are defined as properties added in extensions of
UILayoutGuide on iOS and
NSLayoutGuide on OS X. For example,
Layout guides (conforming to
UIViewController are also supported using the
Relations are expressed using the overloaded operators
Activating Single Constraint
(view1.left == view2.right * 2.0 + 10.0 ~ 750).active = true
Activating Multiple Constraints
NSLayoutConstraint.activateConstraints([ 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.