A UIView extension for common auto layout constraints

UIView+AutoLayout.swift

extension UIView {
    func addConstaintsToPinHorizontalEdgesToSuperView(padding: CGFloat = 0) {
        prepareForConstraints()
        self.superview!.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-(padding)-[view]-(padding)-|",
            options: NSLayoutFormatOptions(0),
            metrics: ["padding":padding],
            views: ["view":self]))
    }
    
    func addConstaintsToPinVerticalEdgesToSuperView(padding: CGFloat = 0) {
        prepareForConstraints()
        self.superview!.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-(padding)-[view]-(padding)-|",
            options: NSLayoutFormatOptions(0),
            metrics: ["padding":padding],
            views: ["view":self]))
    }
    
    func addConstaintsToCenterVertically() {
        prepareForConstraints()
        self.superview!.addConstraint(NSLayoutConstraint(item: self,
            attribute: .CenterY,
            relatedBy: .Equal,
            toItem: self.superview!,
            attribute: .CenterY,
            multiplier: 1.0, constant: 0))
    }
    
    func addConstaintsToCenterHorizontally() {
        prepareForConstraints()
        self.superview!.addConstraint(NSLayoutConstraint(item: self,
            attribute: .CenterX,
            relatedBy: .Equal,
            toItem: self.superview!,
            attribute: .CenterX,
            multiplier: 1.0, constant: 0))
    }
    
    func addConstaintsToPinLeadingToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        prepareForConstraints()
        let constraint = NSLayoutConstraint(item: self,
            attribute: .Leading,
            relatedBy: .Equal,
            toItem: self.superview!,
            attribute: .Leading,
            multiplier: 1, constant: constant)
        
        self.superview!.addConstraint(constraint)
        return constraint
    }
    
    func addConstaintsToPinTrailingToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        prepareForConstraints()
        let constraint = NSLayoutConstraint(item: self,
            attribute: .Trailing,
            relatedBy: .Equal,
            toItem: self.superview!,
            attribute: .Trailing,
            multiplier: 1, constant: constant)
        self.superview!.addConstraint(constraint)
        return constraint
    }
    
    func addConstaintsToPinTopToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        prepareForConstraints()
        let constraint = NSLayoutConstraint(item: self,
            attribute: .Top,
            relatedBy: .Equal,
            toItem: self.superview!,
            attribute: .Top,
            multiplier: 1, constant: constant)
        self.superview!.addConstraint(constraint)
        return constraint
    }
    
    func addConstaintsToPinTopToView(view:UIView,constant: CGFloat) -> NSLayoutConstraint {
        prepareForConstraints()
        let constraint = NSLayoutConstraint(item: self,
            attribute: .Top,
            relatedBy: .Equal,
            toItem: view,
            attribute: .Top,
            multiplier: 1, constant: constant)
        self.superview!.addConstraint(constraint)
        return constraint
    }
    
    func addConstaintsToPinBottomToView(view:UIView,constant: CGFloat) -> NSLayoutConstraint {
        prepareForConstraints()
        let constraint = NSLayoutConstraint(item: self,
            attribute: .Bottom,
            relatedBy: .Equal,
            toItem: view,
            attribute: .Bottom,
            multiplier: 1, constant: constant)
        self.superview!.addConstraint(constraint)
        return constraint
    }
    
    
    func addConstaintsToFillSuperviewWithPadding(padding: CGFloat = 0) {
        prepareForConstraints()
        addConstaintsToPinHorizontalEdgesToSuperView(padding: padding)
        addConstaintsToPinVerticalEdgesToSuperView(padding: padding)
    }
    
    private func prepareForConstraints() {
        self.setTranslatesAutoresizingMaskIntoConstraints(false)
        if superview == nil {
            assert(false, "You need to have a superview before you can add contraints")
        }
    }
}

swift 4.2 update + some refactors to drop force unwraps + accessing functionality through view.layout. pinHorizontalEdgesToSuperView() for example + some smallish refactors:

struct Layout {
    
    let element: UIView
    
    init(_ element: UIView) {
        self.element = element
    }
    
    // MARK: Layout
    
    @discardableResult func pinHorizontalEdgesToSuperView(padding: CGFloat = 0) -> [NSLayoutConstraint] {
        let constraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(padding)-[view]-(padding)-|",
                                                        options: NSLayoutConstraint.FormatOptions(rawValue: 0),
                                                        metrics: ["padding": padding],
                                                        views: ["view": element])
        safeSuperview().addConstraints(constraints)
        return constraints
    }
    
    @discardableResult func pinVerticalEdgesToSuperView(padding: CGFloat = 0) -> [NSLayoutConstraint] {
        let constraints = NSLayoutConstraint.constraints(withVisualFormat: "V:|-(padding)-[view]-(padding)-|",
                                                        options: NSLayoutConstraint.FormatOptions(rawValue: 0),
                                                        metrics: ["padding": padding],
                                                        views: ["view": element])
        safeSuperview().addConstraints(constraints)
        return constraints
    }
    
    @discardableResult func centerVertically() -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .centerY,
                                            relatedBy: .equal,
                                            toItem: safeSuperview(),
                                            attribute: .centerY,
                                            multiplier: 1.0, constant: 0)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func centerHorizontally() -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .centerX,
                                            relatedBy: .equal,
                                            toItem: safeSuperview(),
                                            attribute: .centerX,
                                            multiplier: 1.0, constant: 0)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func pinLeadingToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .leading,
                                            relatedBy: .equal,
                                            toItem: safeSuperview(),
                                            attribute: .leading,
                                            multiplier: 1, constant: constant)
        
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func pinTrailingToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .trailing,
                                            relatedBy: .equal,
                                            toItem: safeSuperview(),
                                            attribute: .trailing,
                                            multiplier: 1, constant: constant)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func pinTopToSuperview(constant: CGFloat) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .top,
                                            relatedBy: .equal,
                                            toItem: safeSuperview(),
                                            attribute: .top,
                                            multiplier: 1, constant: constant)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func pinTopToView(view:UIView,constant: CGFloat) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .top,
                                            relatedBy: .equal,
                                            toItem: view,
                                            attribute: .top,
                                            multiplier: 1, constant: constant)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    @discardableResult func pinBottomToView(view:UIView,constant: CGFloat) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(item: element,
                                            attribute: .bottom,
                                            relatedBy: .equal,
                                            toItem: view,
                                            attribute: .bottom,
                                            multiplier: 1, constant: constant)
        safeSuperview().addConstraint(constraint)
        return constraint
    }
    
    func fillSuperview(padding: CGFloat = 0) {
        safeSuperview()
        pinHorizontalEdgesToSuperView(padding: padding)
        pinVerticalEdgesToSuperView(padding: padding)
    }
    
    @discardableResult private func safeSuperview() -> UIView {
        element.translatesAutoresizingMaskIntoConstraints = false
        guard let view = element.superview else {
            fatalError("You need to have a superview before you can add contraints")
        }
        return view
    }
    
}


extension UIView {
    
    var layout: Layout {
        return Layout(self)
    }
    
}