AutoLayout DSL

Based on this post from SiwftBySundell I've decided to complete the DSL with all the functions offered by the Auto Layout's API, creating some custom operators to complete the functionality.

Layout Anchor operators

Equalization, greater/less than:

view.layout {
	$0.top == otherView.topAnchor
    $0.leading >= otherView.leadingAnchor
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.topAnchor.constraint(equalTo: otherView.topAnchor),
	view.leadingAnchor.constraint(greaterThanOrEqualTo: otherView.leadingAnchor)
])

Equalization, greater/less than with constant value:

view.layout {
    $0.top == otherView.topAnchor - 10.0
    $0.trailing >= otherView.leadingAnchor + 10.0
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.topAnchor.constraint(equalTo: otherView.topAnchor, constant: -10.0),
	view.trailingAnchor.constraint(greaterThanOrEqualTo: otherView.leadingAnchor, constant: 10.0)
])

Center horizontally:

view.layout {
	$0 -|- otherView
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
    view.leadingAnchor.constraint(equalTo: otherView.leadingAnchor),
    view.trailingAnchor.constraint(equalTo: otherView.trailingAnchor)
])

Center horizontally with constant value:

view.layout {
    $0 -|- (otherView + 12.0)
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
    view.leadingAnchor.constraint(equalTo: otherView.leadingAnchor, constant: 12.0),
    view.trailingAnchor.constraint(equalTo: otherView.trailingAnchor, constant: -12.0)
])

Center vertically:

view.layout {
	$0 |-| otherView
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
    view.topAnchor.constraint(equalTo: otherView.topAnchor),
    view.bottomAnchor.constraint(equalTo: otherView.bottomAnchor)
])

Center vertically with constant value:

view.layout {
    $0 |-| (otherView + 12.0)
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
    view.topAnchor.constraint(equalTo: otherView.topAnchor, constant: 12.0),
    view.bottomAnchor.constraint(equalTo: otherView.bottomAnchor, constant: -12.0)
])

Layout Dimension operators

Equalization, greater/less than to constant value:

view.layout {
	$0.height == 120.0
	$0.width >= 100.0
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.heightAnchor.constraint(equalToConstant: 120.0),
	view.widthAnchor.constraint(greaterThanOrEqualToConstant: 100.0)
])

Equalization, greater/less than to other view:

view.layout {
    $0.height == otherView.heightAnchor
    $0.width >= otherView.widthAnchor
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.heightAnchor.constraint(equalTo: otherView.heightAnchor),
	view.widthAnchor.constraint(greaterThanOrEqualTo: otherView.widthAnchor)
])

Equalization, greater/less than to other view with constant value:

view.layout {
    $0.height == otherView.heightAnchor + 20.0
    $0.width >= otherView.widthAnchor - 10.0
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.heightAnchor.constraint(equalTo: otherView.heightAnchor, constant: 20.0),
	view.widthAnchor.constraint(greaterThanOrEqualTo: otherView.widthAnchor, constant: -10.0)
])

Equalization, greater/less than to other view with multiplier:

view.layout {
    $0.height == otherView.heightAnchor * 0.5
    $0.width >= otherView.widthAnchor * 0.5
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.heightAnchor.constraint(equalTo: otherView.heightAnchor, multiplier: 0.5),
	view.widthAnchor.constraint(greaterThanOrEqualTo: otherView.widthAnchor, multiplier: 0.5)
])

Equalization, greater/less than to other view with constant value and multiplier:

view.layout {
    $0.height == otherView.heightAnchor + 20.0 * 0.5
    $0.width >= otherView.widthAnchor - 10.0 * 0.5
}

NSLayoutConstraint equivalent:

NSLayoutConstraint.activate([
	view.heightAnchor.constraint(equalTo: otherView.heightAnchor, multiplier: 0.5, constant: 20.0),
	view.widthAnchor.constraint(greaterThanOrEqualTo: otherView.widthAnchor, multiplier: 0.5, constant: -10.0)
])

Assign width and height value with one operation:

view.layout {
    ($0.width & $0.height) == (24.0 * 24.0)
}

Priority

With the infix operator '~' is possible to define the priority of the created constraint with all the operators. Directly with the UILayoutPriority static values or using a float value.

view.layout {
    $0.top == otherView.topAnchor + 12.0 ~ .defaultLow
    $0.height == otherView.heightAnchor * 0.5 ~ .defaultHigh
    $0.width >= otherView.widthAnchor * 0.5 ~ 750.0
}

NSLayoutConstraint equivalent:

let top = view.topAnchor.constraint(equalTo: otherView.topAnchor, constant: 12.0)
top.priority = .defaultLow
top.isActive = true
let height = view.heightAnchor.constraint(equalTo: otherView.heightAnchor, multiplier: 0.5)
height.priority = .defaultHigh
height.isActive = true
let width = view.widthAnchor.constraint(greaterThanOrEqualTo: otherView.widthAnchor, multiplier: 0.5)
width.priority = UILayoutPriority(750.0)
width.isActive = true

Util functions

Fill

view.fill(otherView)

Layout equivalent:

view.layout {
    $0.top == otherView.top
    $0.bottom == otherView.bottom
    $0.leading == otherView.leading
    $0.trailing == otherView.trailing
}

Fill considering safe area

view.fillSafeArea(otherView)

Layout equivalent:

view.layout {
    $0.top == view.safeAreaLayoutGuide.topAnchor
    $0.bottom == otherView.safeAreaLayoutGuide.bottomAnchor
    $0.leading == otherView.safeAreaLayoutGuide.leadingAnchor
    $0.trailing == otherView.safeAreaLayoutGuide.trailingAnchor
}

Height and width

view.height(100.0)
view.width(100.0)

Center

Centered on other view

view.centerIn(otherView)

Layout equivalent:

view.layout {
    $0.centerX == otherView.centerXAnchor
    $0.centerY == otherView.centerYAnchor
}

Centered axis with padding

view.centerXin(otherView, 10.0)
view.centerYin(otherView)

Layout equivalent:

view.layout {
    $0 -|- (view + 10.0)
}
view.layout {
    $0 |-| view
}