ViewShorthand.swift

extension UIView {
    func constraintsEqualToSuperview(_ edgeInsets: UIEdgeInsets = UIEdgeInsets.zero, priority: UILayoutPriority = 1000) -> [NSLayoutConstraint] {
        self.translatesAutoresizingMaskIntoConstraints = false
        var constraints = [NSLayoutConstraint]()
        if let superview = self.superview {
            constraints.append(self.constraining(.leading, .equal, to: superview, constant: edgeInsets.left, priority: priority))
            constraints.append(self.constraining(.trailing, .equal, to: superview, constant: -edgeInsets.right, priority: priority))
            constraints.append(self.constraining(.top, .equal, to: superview, constant: edgeInsets.top, priority: priority))
            constraints.append(self.constraining(.bottom, .equal, to: superview, constant: -edgeInsets.bottom, priority: priority))
        }
        return constraints
    }
    
    func constraining(_ attribute: NSLayoutAttribute, _ relation: NSLayoutRelation, to constant: CGFloat, multiplier: CGFloat = 1.0, priority: UILayoutPriority = 1000) -> NSLayoutConstraint {
        self.translatesAutoresizingMaskIntoConstraints = false
        let constraint =  NSLayoutConstraint(item: self, attribute: attribute, relatedBy: relation, toItem: nil, attribute: .notAnAttribute, multiplier: multiplier, constant: constant)
        constraint.priority = priority
        return constraint
    }
    
    func constraining(_ attribute: NSLayoutAttribute, _ relation: NSLayoutRelation, to otherAttribute: NSLayoutAttribute, of item: AnyObject? = nil, multiplier: CGFloat = 1.0, constant: CGFloat = 0.0, priority: UILayoutPriority = 1000) -> NSLayoutConstraint {
        self.translatesAutoresizingMaskIntoConstraints = false
        let constraint =  NSLayoutConstraint(item: self, attribute: attribute, relatedBy: relation, toItem: item ?? self, attribute: otherAttribute, multiplier: multiplier, constant: constant)
        constraint.priority = priority
        return constraint
    }
    
    func constraining(_ attribute: NSLayoutAttribute, _ relation: NSLayoutRelation, to item: AnyObject, multiplier: CGFloat = 1.0, constant: CGFloat = 0.0, priority: UILayoutPriority = 1000) -> NSLayoutConstraint {
        self.translatesAutoresizingMaskIntoConstraints = false
        let constraint = NSLayoutConstraint(item: self, attribute: attribute, relatedBy: relation, toItem: item, attribute: attribute, multiplier: multiplier, constant: constant)
        constraint.priority = priority
        return constraint
    }
    
    func constraining(_ attributes: [NSLayoutAttribute], _ relation: NSLayoutRelation, to item: AnyObject, multiplier: CGFloat = 1.0, constant: CGFloat = 0.0, priority: UILayoutPriority = 1000) -> [NSLayoutConstraint] {
        return attributes.map { self.constraining($0, relation, to: item, multiplier: multiplier, constant: constant, priority: priority) }
    }
    
    func constraining(_ attributes: [NSLayoutAttribute], _ relation: NSLayoutRelation, to constant: CGFloat, multiplier: CGFloat = 0.0, priority: UILayoutPriority = 1000) -> [NSLayoutConstraint] {
        return attributes.map { self.constraining($0, relation, to: constant, multiplier: multiplier, priority: priority) }
    }
    
    func constraints(size: CGSize) -> [NSLayoutConstraint] {
        return [
            constraining(.width, .equal, to: size.width),
            constraining(.height, .equal, to: size.height)
        ]
    }
}

extension NSLayoutConstraint {
    class func constraints(format: String, options: NSLayoutFormatOptions = NSLayoutFormatOptions(), metrics: [String: Any]? = nil, views: [String: Any] = [:]) -> [NSLayoutConstraint] {
        return NSLayoutConstraint.constraints(withVisualFormat: format, options: options, metrics: metrics, views: views) 
    }
}

Usage:

NSLayoutConstraint.activate(subview.constraintsEqualToSuperview())
subview.constraining(.height, .equal, to: 25.0).isActive = true
subview2.constraining(.height, .lessThanOrEqual, to: subview).isActive = true
NSLayoutConstraint.activate(
  subview3.constraining([.width, .centerY], equal, to: subview))