Set up your Auto Layout constraints declaratively and without any stringly typing!

Call the layout function with your UIView or NSView instances as well as a closure in which you declare the constraints between the different attributes of your views:

layout(view1, view2) { view1, view2 in
    view1.width   == (view1.superview!.width - 50) * 0.5
    view2.width   == view1.width - 50
    view1.height  == 40
    view2.height  == view1.height
    view1.centerX == view1.superview!.centerX
    view2.centerX == view1.centerX

    view1.top >= view1.superview!.top + 20
    view2.top == view1.bottom + 20
}

Cartography supports all built-in attributes as of iOS 7 and OS X 10.9, those are: width, height, top, right bottom, left, leading, trailing, centerX, centerY and baseline. These can be further refined using the following operators: *, /, + and -.

Additionally, it supports convenient compound attributes that allow you to assign multiple attributes at once:

layout(view) { view in
    view.size   == view.superview!.size / 2
    view.center == view.superview!.center
}

layout(view) { view in
    view.edges == inset(view.superview!.edges, 20, 20, 40, 20); return
}

(We need to return explicitly here to work around a bug in Swift, this only affects single line blocks, however.)

You can set the priorities of your constraints using the ~ operator:

layout(view) { view in
    view.width  >= 200 ~ 100
    view.height >= 200 ~ 100
}

Since the ==, >=, <= and ~ emit NSLayoutConstraint instances, you can capture their results if you need to refer to the layout constraints at a later time:

var width: NSLayoutConstraint?

layout(view) { view in
    width = (view.width == 200 ~ 100); return
}

Note that declaring compound attributes returns multiple constraints at once:

var constraints: NSLayoutConstraint[]?

layout(view) { view in
    constraints = (view.size == view.superview!.size ~ 100); return
}

Cartography is written in Swift so it"s pretty much beta by definition. It was inspired by the excellent FLKAutoLayout by Florian Kugler.