/SwiftLayoutConstraints

Expressive NSLayoutConstraint for Swift

Primary LanguageSwiftMIT LicenseMIT

SwiftLayoutConstraints

CI Status Carthage compatible Version License Platform

SwiftLayoutConstraints aims to provide expressive NSLayoutConstraint with Swift.

Compatibility

SwiftLayoutConstraints targets Swift 2.2 and iOS 8

Constraints

Basic Constraints can be made such as:

// assume we have 2 views and they are added to one parent (view)
let view1 = UIView()
view1.translatesAutoresizingMaskIntoConstraints = false
view1.backgroundColor = UIColor.greenColor()
let view2 = UIView()
view2.translatesAutoresizingMaskIntoConstraints = false
view2.backgroundColor = UIColor.blueColor()
view.addSubview(view1)
view.addSubview(view2)

// Expressions below create, **activate** and return constraints
view1.ls_top | .Left | .Right | view2.ls_left | .Right | .Bottom ~== view
view2.ls_top ~== view1.ls_bottom + 40
view1.ls_height ~== view.ls_height * 0.25 + 50

The above code generates this output:
Example

Overview

LayoutConstraints are represented as LayoutConstraintType, and has two implementations:

  1. LhsLayoutConstraint represents left-hand side, and does NOT support mutating its constant and multiplier.
  2. RhsLayoutConstraint represents right-hand side, and supports mutating its constant and multiplier.

Relation Operators

SwiftLayoutConstraints introduces operators to represent each NSLayoutRelation, simply ~ is added before the expressive form of the relation.

  • ~== for NSLayoutRelation.Equal
  • ~>= for NSLayoutRelation.GreaterThanOrEqual
  • ~<= for NSLayoutRelation.LessThanOrEqual

Supported Expressions

Representing any Relation Operator as :op, the following expressions are supported:

LhsLayoutConstraint :op LayoutConstraintType
LhsLayoutConstraint :op CGFloat
[LhsLayoutConstraint] :op AnyObject
AnyObject :op [LayoutConstraintType]
[LhsLayoutConstraint] :op [LayoutConstraintType]

Quick Notes

  1. At any point, Left-hand side of any expression is always LhsLayoutConstraint
  2. You may create an array of constraints using | operator, i.e: view.ls_height | view.ls_width
  3. Operator | also accepts NSLayoutAttribute where values (object, constant and multiplier) are taken from previous constraint, i.e: view.ls_top | .Bottom
  4. You may use + or * to set constraint's constant and multiplier, i.e: view1.ls_top ~== view2.ls_bottom * 1 + 20
  5. Consider operators precedence in your expressions, i.e: view.ls_top * 0.5 + 50 is not same as view.ls_top + 50 * 0.5

Installation

Carthage

github "ahmadbaraka/SwiftLayoutConstraints" ~> 1.0

Cocoapods

pod 'SwiftLayoutConstraints', '~> 1.0'

License

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