KVConstraintKit

KVConstraintKit is a DSL to make easy & impressive Auto Layout constraints on iOS, tvOS & OSX with Swift

Installation

Using CocoaPods

1. To integrate KVConstraintKit into your Xcode project using CocoaPods, specify it to a target in your Podfile:

use_frameworks!
pod 'KVConstraintKit', '~> 2.1'

If you want to be on the bleeding edge, replace the last line with:

pod 'KVConstraintKit', :git => 'https://github.com/keshavvishwkarma/KVConstraintKit.git', :branch => 'master'

2. Run pod install and open the open the {Project}.xcworkspace instead of the {Project}.xcodeproj file to launch Xcode.

Using Carthage

1. To integrate KVConstraintKit into your Xcode project using Carthage, specify it in your Cartfile:

github "keshavvishwkarma/KVConstraintKit" ~> 2.1

2. Run carthage update and follow the additional steps in order to add KVConstraintKit to your project.

Auto Layout Attributes

KVConstraintKit supports all built-in layout attributes as of iOS, tvOS & OSX, see the NSLayoutAttribute enum.

Usage

Here's a quick example:

Without Using KVConstraintKit

let v = UIView.prepareAutoLayoutView()
v.backgroundColor = UIColor.red
view.addSubview(v)

// Prepare constraints and then add them on superview of view
let top = NSLayoutConstraint( item: v, attribute: .top,
                         relatedBy: .equal,
                            toItem: v.superview!, attribute: .top,
                        multiplier: 1.0, constant: 0)

let leading = NSLayoutConstraint( item: v, attribute: .leading,
                             relatedBy: .equal,
                                toItem: v.superview!, attribute: .leading,
                            multiplier: 1.0, constant: 0)

let trailing = NSLayoutConstraint( item: v, attribute: .trailing,
                         relatedBy: .equal,
                            toItem: v.superview!, attribute: .trailing,
                        multiplier: 1.0, constant: 0)

let bottom = NSLayoutConstraint( item: v, attribute: .bottom,
                         relatedBy: .equal,
                            toItem: v.superview!, attribute: .bottom,
                        multiplier: 1.0, constant: 0)

v.superview?.addConstraints([top, leading, trailing, bottom])

Using KVConstraintKit

v +== [.top, .leading, .trailing, .bottom]

Similarly for margin constraints

v +== [ .leadingMargin, .trailingMargin, .topMargin, .bottomMargin]

Fit

Horizontally

view.fitHorizontallyToSuperview()
OR
view.fitHorizontallyToSuperview(20) // padding

Vertically

view.fitVerticallyToSuperview()
OR
view.fitVerticallyToSuperview(20) // padding

Horizontally & Vertically

view.fitToSuperview()
OR
view.fitToSuperview(20) // width same padding for all edge

Fit with inset

let inset = UIEdgeInsets(top: 4, left: 8, bottom: 12, right: 16)    
view.fitToSuperview(contentInset:inset)

Center

Horizontally

view.applyCenterX()
OR
view.applyCenterX(20) // X offset

Vertically

view.applyCenterY()
OR
view.applyCenterY(20) // Y offset

Horizontally & Vertically

view.applyCenter()
OR
view.applyCenter(CGPoint(x:20, y:20)) // XY offset
OR
view.applyCenterX(4).applyCenterY(16) // XY offset

Size

Width

view.applyWidth(100)
OR
view.applyAtLeastWidth(100)
OR
view.applyAtMostWidth(100)

Height

view.applyHeight(100)
OR
view.applyAtLeastHeight(100)
OR
view.applyAtMostHeight(100)

Aspact Ratio

view.applyAspectRatio()

Quick Reference

Layout Attributes	Using Operator	Using Method
Leading	(subview +== .leading).constant = 20	subview.applyLeading(20)
Trailing	(subview +== .trailing).constant = 20	subview.applyTrailing(20)
Top	(subview +== .top).constant = 20	subview.applyTop(20)
Bottom	(subview +== .bottom).constant = 20	subview.applyBottom(20)
CenterX	subview +== .centerX	subview.applyCenterX()
CenterY	subview +== .centerY	subview.applyCenterY()
Height	subview +== (.height, 100)	subview.applyHeight(100)
Width	subview +== (.width, 100)	subview.applyWidth(100)
CenterX & CenterY	subview +== [.centerX, .centerY]	subview.applyCenter()

For more details see the ApplyViewConstraint extension and LayoutRelationable Protocol of KVConstraintKit.

Note: Avoid using Left and Right attributes. Use Leading and Trailing instead. This allows the layout to adapt to the view’s reading direction. By default the reading direction is determined based on the current language set by the user.

Custom Operators

The following types of operators are provided by KVConstraintKit, to add, remove, access and modify constraints.

Operator	Meaning
+	to add constraint
-	to remove constraint
*	to modify multiplier of constraint
~	to modify Priority ( UILayoutPriority ), Relation ( NSLayoutRelation ) & Replace constraint
<-	to access constraint by attributes ( eg. NSLayoutAttribute.Height )
+==	to add equal relation ( NSLayoutRelation.Equal ) constraint
+>=	to add greater than or equal relation ( NSLayoutRelation.GreaterThanOrEqual ) constraint
+<=	to add less than or equal relation ( NSLayoutRelation.LessThanOrEqual ) constraint
*==	to add equal relation constraint with multiplier
*>=	to add greater than or equal relation constraint with multiplier
*<=	to add less than or equal relation constraint with multiplier
|==|	to add or equal relation constraint between sibling views
|>=|	to add greater than or equal relation constraint between sibling views
|<=|	to add less than or equal relation constraint between sibling views

License

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

Contributions

Any contribution is more than welcome! You can contribute through pull requests and issues on GitHub.

Author

If you wish to contact me, email at: keshavvbe@gmail.com