SwiftLayoutConstraints aims to provide expressive NSLayoutConstraint with Swift.

SwiftLayoutConstraints targets Swift 2.2 and iOS 8

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:

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.

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

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]

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

github "ahmadbaraka/SwiftLayoutConstraints" ~> 1.0

pod 'SwiftLayoutConstraints', '~> 1.0'

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