🧲 Mag

Mag is Framework which wraps NSLayoutAnchor.

Installation

CocoaPods

Add the following to your Podfile:

pod "Mag"

Carthage

Add the following to your Cartfile:

github "cats-oss/Mag"

Example

let redView = UIView(frame: .zero)
redView.backgroundColor = .red
view.addSubview(redView)
redView.sizeAnchor == CGSize(width: 100, height: 100)
redView.leadingAnchor == view.leadingAnchor + 100
redView.topAnchor == (view.bottomAnchor - 100) * 0.5 ~ 999

let label = UILabel(frame: .zero)
label.text = "Example"
label.textAlignment = .center
redView.addSubview(label)
label.edgeAnchor == redView.edgeAnchor

let blueView = UIView(frame: .zero)
blueView.backgroundColor = .blue
view.addSubview(blueView)
blueView.sizeAnchor == redView.sizeAnchor
blueView.centerAnchor == redView.centerAnchor + CGPoint(x: 100, y: -100)

Usage

Alignment

redView.leadingAnchor == view.leadingAnchor + 10
// redView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 10)

redView.topAnchor >= view.bottomAnchor
// redView.topAnchor.constraint(greaterThanOrEqualTo: view.bottomAnchor, constant: 0)

redView.centerYAnchor <= view.centerYAnchor - 20
// redView.centerYAnchor.constraint(lessThanOrEqualTo: view.centerYAnchor, constant: -20)

blueView.centerAnchor == redView.centerAnchor + CGPoint(x: 100, y: -100)
// blueView.centerXAnchor.constraint(equalTo: redView.centerXAnchor, constant: 100)
// blueView.centerYAnchor.constraint(equalTo: redView.centerYAnchor, constant: -100)

label.horizontalAnchor == redView.horizontalAnchor + UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10)
// label.leadingAnchor.constraint(equalTo: redView.leadingAnchor, constant: 10)
// label.trailingAnchor.constraint(equalTo: redView.trailingAnchor, constant: -10)

label.verticalAnchor == redView.verticalAnchor + UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10)
// label.topAnchor.constraint(equalTo: redView.topAnchor, constant: 5),
// label.bottomAnchor.constraint(equalTo: redView.bottomAnchor, constant: -5)

label.edgeAnchor == redView.edgeAnchor + UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10)
// label.topAnchor.constraint(equalTo: redView.topAnchor, constant: 5),
// label.bottomAnchor.constraint(equalTo: redView.bottomAnchor, constant: -5)
// label.leadingAnchor.constraint(equalTo: redView.leadingAnchor, constant: 10)
// label.trailingAnchor.constraint(equalTo: redView.trailingAnchor, constant: -10)

redView.topAnchor == view.bottomAnchor * 0.5
// redView.topAnchor.constraint(equalTo: view.bottomAnchor, constant: 0)
// multiplying 0.5

Size

redView.widthAnchor == 100
// redView.widthAnchor.constraint(equalToConstant: 100)

redView.heightAnchor >= 200
// redView.heightAnchor.constraint(greaterThanOrEqualToConstant: 200)

redView.widthAnchor <= 200
// redView.widthAnchor.constraint(lessThanOrEqualToConstant: 200)

redView.sizeAnchor == CGSize(width: 100, height: 200)
// redView.widthAnchor.constraint(equalToConstant: 100)
// redView.heightAnchor.constraint(equalToConstant: 200)

blueView.sizeAnchor <= redView.sizeAnchor + CGSize(width: 20, height: 0)
// blueView.widthAnchor.constraint(lessThanOrEqualTo: redView.widthAnchor, constant: 20)
// blueView.heightAnchor.constraint(lessThanOrEqualTo: redView.heightAnchor, constant: 0)

redView.sizeAnchor == view.sizeAnchor * 0.5
// redView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.5, constant: 0)
// redView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5, constant: 0)

Priority

redView.topAnchor == view.topAnchor ~ .defaultHigh
// constraint.priority = .defaultHigh

redView.centerAnchor == view.centerAnchor ~ 900
// constraint.priority = UILayoutPriority(Float(900)) (or NSLayoutConstraint.Priority)

Constraints

Comparison operators return NSLayoutConstraint.

let constraint = redView.leadingAnchor == view.leadingAnchor
// returns NSLayoutConstraint
constraint.isActive = true

If target anchors are composite anchors, returns multiple NSLayoutConstraint. (e.g. [NSLayoutConstraint])

let constraints = redView.centerAnchor == view.centerAnchor
// returns [NSLayoutConstraint]
NSLayoutConstraint.activate(constraints)

If firstItem in NSLayoutConstraint is UIView (or NSView), translatesAutoresizingMaskIntoConstraints is set to false.

Activation

Comparison operators return NSLayoutConstraint which has never activated.

If the constraint deinits without being activated, it activates automatically.

_ = redView.leadingAnchor == view.leadingAnchor
// NSLayoutConstraint activates automatically

If you want to activate manually, set true to isActivate or executes activate methods.

Singular Constraint

var constraint: NSLayoutConstraint? {
    didSet {
        oldValue?.isActivate = false
        constraint?.isActivate = true
    }
}

constraint = redView.leadingAnchor == view.leadingAnchor

Multiple Constraints

Mag extends NSLayoutConstraint deactivate and activate method.

var constraints: [NSLayoutConstraint] = [] {
    didSet {
        NSLayoutConstraint.deactivate(oldValue, beforeActivate: constraints)
    }
}

constraints = redView.centerAnchor == view.centerAnchor

The following process is the same.

var constraints: [NSLayoutConstraint] = []
constraints.replaceActivatedConstraints(redView.centerAnchor == view.centerAnchor)

LICENSE

Under the MIT license. See LICENSE file for details.