Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Auto Layout DSL
import UIKit
/// Represents a single `NSLayoutConstraint`
enum LayoutAnchor {
case constant(attribute: NSLayoutConstraint.Attribute,
relation: NSLayoutConstraint.Relation,
constant: CGFloat)
case relative(attribute: NSLayoutConstraint.Attribute,
relation: NSLayoutConstraint.Relation,
relatedTo: NSLayoutConstraint.Attribute,
multiplier: CGFloat,
constant: CGFloat)
}
// MARK: - Factory methods
extension LayoutAnchor {
static let leading = relative(attribute: .leading, relation: .equal, relatedTo: .leading)
static let trailing = relative(attribute: .trailing, relation: .equal, relatedTo: .trailing)
static let top = relative(attribute: .top, relation: .equal, relatedTo: .top)
static let bottom = relative(attribute: .bottom, relation: .equal, relatedTo: .bottom)
static let centerX = relative(attribute: .centerX, relation: .equal, relatedTo: .centerX)
static let centerY = relative(attribute: .centerY, relation: .equal, relatedTo: .centerY)
static let width = constant(attribute: .width, relation: .equal)
static let height = constant(attribute: .height, relation: .equal)
static func constant(
attribute: NSLayoutConstraint.Attribute,
relation: NSLayoutConstraint.Relation
) -> (CGFloat) -> LayoutAnchor {
return { constant in
.constant(attribute: attribute, relation: relation, constant: constant)
}
}
static func relative(
attribute: NSLayoutConstraint.Attribute,
relation: NSLayoutConstraint.Relation,
relatedTo: NSLayoutConstraint.Attribute,
multiplier: CGFloat = 1
) -> (CGFloat) -> LayoutAnchor {
return { constant in
.relative(attribute: attribute, relation: relation, relatedTo: relatedTo, multiplier: multiplier, constant: constant)
}
}
}
// MARK: - Conveniences
extension UIView {
func addSubview(_ subview: UIView, anchors: [LayoutAnchor]) {
subview.translatesAutoresizingMaskIntoConstraints = false
addSubview(subview)
subview.activate(anchors: anchors, relativeTo: self)
}
func activate(anchors: [LayoutAnchor], relativeTo item: UIView? = nil) {
let constraints = anchors.map { NSLayoutConstraint(from: self, to: item, anchor: $0) }
NSLayoutConstraint.activate(constraints)
}
}
extension NSLayoutConstraint {
convenience init(from: UIView, to item: UIView?, anchor: LayoutAnchor) {
switch anchor {
case let .constant(attribute: attr, relation: relation, constant: constant):
self.init(
item: from,
attribute: attr,
relatedBy: relation,
toItem: nil,
attribute: .notAnAttribute,
multiplier: 1,
constant: constant
)
case let .relative(attribute: attr,
relation: relation,
relatedTo: relatedTo,
multiplier: multiplier,
constant: constant):
self.init(
item: from,
attribute: attr,
relatedBy: relation,
toItem: item,
attribute: relatedTo,
multiplier: multiplier,
constant: constant
)
}
}
}
import UIKit
class ExampleViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let yellow = UIView()
yellow.backgroundColor = .yellow
view.addSubview(yellow, anchors: [.leading(0), .trailing(0), .bottom(0), .top(0)])
let redBox = UIView()
redBox.backgroundColor = .red
view.addSubview(redBox, anchors: [.centerX(0), .centerY(0), .width(100), .height(100)])
}
}

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to https://unlicense.org

@V8tr
Copy link
Author

V8tr commented Jan 11, 2021

The code is available under the “Unlicense”, which allows you to do whatever you want with it.

@vburojevic
Copy link

vburojevic commented Feb 25, 2021

What if you need to pin something to the safeAreaLayoutGuide?

@devhamza97
Copy link

devhamza97 commented Apr 28, 2021

What if you need to pin something to the safeAreaLayoutGuide?

did you find the solution ?

@prokhorovxo
Copy link

prokhorovxo commented Feb 13, 2022

@vburojevic @devhamza97

This is my approach:

1. Add new case in LayoutAnchor

case relativeSafeArea(attribute: NSLayoutConstraint.Attribute,
                          relation: NSLayoutConstraint.Relation,
                          relatedTo: NSLayoutConstraint.Attribute,
                          multiplier: CGFloat,
                          constant: CGFloat)

2. Add new method in LayoutAnchor

    static func relativeSafeArea(attribute: NSLayoutConstraint.Attribute,
                                 relation: NSLayoutConstraint.Relation,
                                 relatedTo: NSLayoutConstraint.Attribute,
                                 multiplier: CGFloat = 1.0) -> (CGFloat) -> LayoutDSLAnchor {
        return { constant in
                .relativeSafeArea(attribute: attribute,
                                  relation: relation,
                                  relatedTo: relatedTo,
                                  multiplier: multiplier,
                                  constant: constant)
        }
    }

3. Handle new case in convenience init NSLayoutConstraint

case let .relativeSafeArea(attribute: attr,
                                   relation: relation,
                                   relatedTo: relatedTo,
                                   multiplier: multiplier,
                                   constant: constant):
            guard let safeAreaLayoutGuide = item?.safeAreaLayoutGuide
            else { fatalError("\(String(describing: item)) safeAreaLayoutGuide problem") }
            
            self.init(item: from,
                      attribute: attr,
                      relatedBy: relation,
                      toItem: safeAreaLayoutGuide,
                      attribute: relatedTo,
                      multiplier: multiplier,
                      constant: constant)

4. And finally add new static properties in LayoutAnchor

static let leadingSafeArea = relativeSafeArea(attribute: .leading, relation: .equal, relatedTo: .leading)
static let trailingSafeArea = relativeSafeArea(attribute: .trailing, relation: .equal, relatedTo: .trailing)
static let topSafeArea = relativeSafeArea(attribute: .top, relation: .equal, relatedTo: .top)
static let bottomSafeArea = relativeSafeArea(attribute: .bottom, relation: .equal, relatedTo: .bottom)

@nikitatroin
Copy link

nikitatroin commented Feb 16, 2022

@prokhorovxo
Copy link

prokhorovxo commented Feb 22, 2022

@nikitatroin you forgot to use value binding

Screenshot 2022-02-22 at 20 10 39

@nikitatroin
Copy link

nikitatroin commented Feb 22, 2022

@prokhorovxo Oh, thanks man!

@KarthikSaminathan
Copy link

KarthikSaminathan commented Mar 18, 2022

It helped me lot. How i can update the existing layoutanchor? like the same top layoutanchor value needs to be change in the landscape mode? please help

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment