Kolos65/ClosureLayout

A lightweight DSL for simple auto layout in Swift.

A lightweight DSL for simple auto layout in Swift.

Usage

ClosureLayout enables you to create and activate constraints by passing a simple closure to a function called layout. ClosureLayout makes sure to call translatesAutoresizingMaskIntoConstraints = false so you can omit that line too. Using simple operators in the layout closure, you can define constraints like this:

label.layout {
    $0.top == view.topAnchor + 30
    $0.leading == view.leadingAnchor + 20
    $0.size == CGSize(width: 200, height: 40)
}

button.layout {
    $0.width == otherView.widthAnchor - 40
    $0.height == otherView.heightAnchor + 10
    $0.centerX == otherView.centerXAnchor
    $0.centerY == otherView.centerYAnchor
}

Instead of writing this:

label.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
    label.topAnchor.constraint(equalTo: view.topAnchor, constant: 30),
    label.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
    label.widthAnchor.constraint(equalToConstant: 200),
    label.heightAnchor.constraint(equalToConstant: 40)
])

button.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
    button.widthAnchor.constraint(equalTo: otherView.widthAnchor, constant: -40),
    button.heightAnchor.constraint(equalTo: otherView.heightAnchor, constant: 10),
    button.centerXAnchor.constraint(equalTo: otherView.centerXAnchor),
    button.centerYAnchor.constraint(equalTo: otherView.centerYAnchor)
])

Furthermore, the library contains a convenient way of defining boilerplate constraints. When using auto layout, you often need to constrain every edge of a subview to its superview. You might create a wrapper for a label in a table view header or fill a transparent view with blur, etc... In these cases, you can use a single method to create the desired constraints:

wrapper.fillWith(subview)

is equal to:

wrapper.addSubview(subview)
subview.translatesAutoresizingMaskIntoConstraints = false
subview.topAnchor.constraint(equalTo: wrapper.topAnchor).isActive = true
subview.bottomAnchor.constraint(equalTo: wrapper.bottomAnchor).isActive = true
subview.leadingAnchor.constraint(equalTo: wrapper.leadingAnchor).isActive = true
subview.trailingAnchor.constraint(equalTo: wrapper.trailingAnchor).isActive = true

You can optianally provide insets to this function, which will set the given constants on the corresponding constraints:

let insets = UIEdgeInsets(top: 20, left: 20, bottom: 20, right: 20)
wrapper.fillWith(subview, insets: insets)

If you need a reference to one of the constraints you can get them from the tuple returned by the function.

let constraints = wrapper.fillWith(subview)
self.subviewTopConstraint = constraints.top

Installation

ClosureLayout is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'ClosureLayout'

Credits

ClosureLayout is based on an article, written by John Sundell. Listen to his podcast on Apple Podcasts and check out his website for more awesome content on Swift development.

License

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