UIButton+Constraints.swift

import UIKit

extension UIButton {
    var topConstraints: [NSLayoutConstraint]? {
        return self.superview?.constraints.filter( { ($0.firstItem as? UIButton == self && $0.firstAttribute == .top) || ($0.secondItem as? UIButton == self && $0.secondAttribute == .top) })
    }
    var leftConstraints: [NSLayoutConstraint]? {
        return self.superview?.constraints.filter( { ($0.firstItem as? UIButton == self && $0.firstAttribute == .left) || ($0.secondItem as? UIButton == self && $0.secondAttribute == .left) })
    }
    var rightConstraints: [NSLayoutConstraint]? {
        return self.superview?.constraints.filter( { ($0.firstItem as? UIButton == self && $0.firstAttribute == .right) || ($0.secondItem as? UIButton == self && $0.secondAttribute == .right) })
    }
    var bottomConstraints: [NSLayoutConstraint]? {
        return self.superview?.constraints.filter( { (($0.firstItem as? UIButton) == self && $0.firstAttribute == .bottom) || (($0.secondItem as? UIButton == self) && $0.secondAttribute == .bottom) })
    }
}