NSRegularExpression w/ Swift 2.0; Two cases: 1) w/ catch-all” block 2) w/ "forced-try"

MYNSRegularExpressionInitExample.swift

var input: String

// CASE 1
func validateWithError(error: NSErrorPointer) -> Bool {
  var regexpError: NSError?
  let regexp: NSRegularExpression?
  do {
    regexp = try NSRegularExpression(pattern: "[a-zA-Z0-9_]{4,}", options:[])
  } catch let error as NSError {
      regexpError = error
      regexp = nil
  }
  if regexp != nil {
  // validation
    let inputRange = NSRange(location:0, length: nonEmptyInput.characters.count )
    let result = regexp!.rangeOfFirstMatchInString(nonEmptyInput, options: .Anchored, range: inputRange)
    if result.location == NSNotFound  {
      return false
    }
    else {
      return true
    }
  }
  else {
    // regexp was not initialized
    if error != nil { error.memory = regexpError }
    return false
  }
}

// CASE 2
func validateWithError(error: NSErrorPointer) -> Bool {
    let regexp = try! NSRegularExpression(pattern: "[a-zA-Z0-9_]{4,}", options: [])
    let inputRange = NSRange(location:0, length: nonEmptyInput.characters.count )
    let result = regexp.rangeOfFirstMatchInString(nonEmptyInput, options: .Anchored, range: inputRange)
    if result.location == NSNotFound  {
        // regexp validation failed
        // TODO: create error object for it
        return false
    }
    else {
        return true
    }
}