UIKit extensions

##UIView

       // Apply constraints to current view relative to another view, by default it is superview.
    public func applyConstraints(
        relativeToView view: UIView? = nil,
        leading: CGFloat? = nil,
        trailing: CGFloat? = nil,
        top: CGFloat? = nil,
        bottom: CGFloat? = nil,
        centerX: CGFloat? = nil,
        centerY: CGFloat? = nil,
        width: CGFloat? = nil,
        height: CGFloat? = nil
    ) {
        self.translatesAutoresizingMaskIntoConstraints = false
        var parentView = view
        if parentView == nil {
            parentView = self.superview
        }
        if let view = parentView {
            if let leading = leading {
                leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: leading).isActive = true
            }
            if let trailing = trailing {
                trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: trailing).isActive = true
            }
            if let top = top {
                topAnchor.constraint(equalTo: view.topAnchor, constant: top).isActive = true
            }
            if let bottom = bottom {
                bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: bottom).isActive = true
            }
            if let centerX = centerX {
                centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: centerX).isActive = true
            }
            if let centerY = centerY {
                centerYAnchor.constraint(equalTo: view.centerYAnchor, constant: centerY).isActive = true
            }
        }
        if let width = width {
            widthAnchor.constraint(equalToConstant: width).isActive = true
        }
        if let height = height {
            heightAnchor.constraint(equalToConstant: height).isActive = true
        }
    }
    
    // Apply constraints to current view relative to another anchor.
    public func applyConstraints(
        leadingAnchor: NSLayoutAnchor<NSLayoutXAxisAnchor>? = nil,
        leadingValue: CGFloat? = nil,
        trailingAnchor: NSLayoutAnchor<NSLayoutXAxisAnchor>? = nil,
        trailingValue: CGFloat? = nil,
        topAnchor: NSLayoutAnchor<NSLayoutYAxisAnchor>? = nil,
        topValue: CGFloat? = nil,
        bottomAnchor: NSLayoutAnchor<NSLayoutYAxisAnchor>? = nil,
        bottomValue: CGFloat? = nil,
        centerXAnchor: NSLayoutAnchor<NSLayoutXAxisAnchor>? = nil,
        centerXValue: CGFloat? = nil,
        centerYAnchor: NSLayoutAnchor<NSLayoutYAxisAnchor>? = nil,
        centerYValue: CGFloat? = nil,
        widthAnchor: NSLayoutAnchor<NSLayoutDimension>? = nil,
        widthValue: CGFloat? = nil,
        heightAnchor: NSLayoutAnchor<NSLayoutDimension>? = nil,
        heightValue: CGFloat? = nil
    ) {
        self.translatesAutoresizingMaskIntoConstraints = false
        if let topAnchor = topAnchor {
            self.topAnchor.constraint(equalTo: topAnchor, constant: topValue ?? 0).isActive = true
        }
        if let bottomAnchor = bottomAnchor {
            self.bottomAnchor.constraint(equalTo: bottomAnchor, constant: bottomValue ?? 0).isActive = true
        }
        if let leadingAnchor = leadingAnchor {
            self.leadingAnchor.constraint(equalTo: leadingAnchor, constant: leadingValue ?? 0).isActive = true
        }
        if let trailingAnchor = trailingAnchor {
            self.trailingAnchor.constraint(equalTo: trailingAnchor, constant: trailingValue ?? 0).isActive = true
        }
        if let widthAnchor = widthAnchor {
            self.widthAnchor.constraint(equalTo: widthAnchor, constant: widthValue ?? 0).isActive = true
        }
        if let heightAnchor = heightAnchor {
            self.heightAnchor.constraint(equalTo: heightAnchor, constant: heightValue ?? 0).isActive = true
        }
        if let centerXAnchor = centerXAnchor {
            self.centerXAnchor.constraint(equalTo: centerXAnchor, constant: centerXValue ?? 0).isActive = true
        }
        if let centerYAnchor = centerYAnchor {
            self.centerYAnchor.constraint(equalTo: centerYAnchor, constant: centerYValue ?? 0).isActive = true
        }
    }