      - Returns: The leading NSLayoutConstraint if found.
      */
     public var leadingConstraint: NSLayoutConstraint? {
-        return constraintForView(self, attribute: .leading, existsOnView: self.superview)
+        return constraintForView(self, attribute: .leading, existsOnView: superview)
     }
     
 }

    - Returns: The top NSLayoutConstraint if found.
     */
    public var topConstraint: NSLayoutConstraint? {
        return constraintForView(self, attribute: .top, existsOnView: self.superview)
    }
    
    /** Gets the bottom constraint if found.

    - Returns: The right NSLayoutConstraint if found.
     */
    public var rightConstraint: NSLayoutConstraint? {
        return constraintForView(self, attribute: .right, existsOnView: superview)
    }
        
    /** Gets the top constraint if found.
