Stacks and Spacers

spacers.swift

public typealias Stack = UIStackView

public extension Stack {
    @nonobjc public convenience init(_ views: UIView..., with: (UIStackView) -> Void = { _ in }) {
        self.init(arrangedSubviews: views)
        with(self)
    }

    @nonobjc public convenience init(_ views: [UIView], axis: UILayoutConstraintAxis = .horizontal, spacing: CGFloat = 0, alignment: UIStackViewAlignment = .fill, distribution: UIStackViewDistribution = .fill) {
        self.init(arrangedSubviews: views)
        self.axis = axis
        self.spacing = spacing
        self.alignment = alignment
        self.distribution = distribution
    }
  
    @nonobjc public convenience init(style: ((UIStackView) -> Void)..., views: [UIView]) {
        self.init(arrangedSubviews: views)
        style.forEach { $0(self) }
    }
}

public final class Spacer: UIView { // using `UIView` and not `UILayoutGuide` to support stack views
    @nonobjc public convenience init(width: CGFloat) { self.init(.width(width)) }
    @nonobjc public convenience init(minWidth: CGFloat) { self.init(.width(minWidth), isFlexible: true) }
    @nonobjc public convenience init(height: CGFloat) { self.init(.height(height)) }
    @nonobjc public convenience init(minHeight: CGFloat) { self.init(.height(minHeight), isFlexible: true) }

    private enum Dimension {
        case width(CGFloat), height(CGFloat)
    }

    private init(_ dimension: Dimension, isFlexible: Bool = false) {
        super.init(frame: .zero)
        Constraints(for: self) {
            switch dimension {
            case let .width(width):
                $0.width.set(width, relation: isFlexible ? .greaterThanOrEqual : .equal)
                if isFlexible { $0.width.set(width).priority = UILayoutPriority(42) } // disambiguate
                $0.height.set(0).priority = UILayoutPriority(42)  // disambiguate
            case let .height(height):
                $0.height.set(height, relation: isFlexible ? .greaterThanOrEqual : .equal)
                if isFlexible { $0.height.set(height).priority = UILayoutPriority(42) } // disambiguate
                $0.width.set(0).priority = UILayoutPriority(42) // disambiguate
            }
        }
    }

    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    // don't draw anything
    override public class var layerClass: AnyClass { return CATransformLayer.self }
    override public var backgroundColor: UIColor? { get { return nil } set { return } }
}

// MARK: Insets

public typealias Insets = UIEdgeInsets
public extension UIEdgeInsets {
    public init(_ all: CGFloat) { self = UIEdgeInsetsMake(all, all, all, all) }
}