Easy access to constraints by Identifier

UIView+Contstraints.swift

//
//  UIView+Contstraints.swift
//
//  HOW TO USE
//  1. Setup constraints and define NSLayoutConstraint.identifier
//  2. Use identifier as parameter for call
//  3. Call on superview: if let constraint = self.view.constraintByStringId("Id") { } 
//  4. Change, animate or replace constraint

import Foundation
import UIKit

extension UIView {
  func constraintByStringId(stringId: String) -> NSLayoutConstraint? {
    for constraint in self.constraints {
      if constraint.identifier == stringId {
        return constraint
      }
    }
    return nil
  }
  
  func constraintsByStringId(stringId: String) -> [NSLayoutConstraint]? {
    var result = [NSLayoutConstraint]()
    for constraint in self.constraints {
      if constraint.identifier == stringId {
        result.append(constraint)
      }
    }
    return result.count == 0 ? nil : result
  }
}