#REGEX VALIDATOR HOW TO#
#REGEX VALIDATOR CODE#

“Lemme see-I can try to split the string, and use a catch if it fails. My breaking point came this past week, as I wrote yet another complicated method to validate a comma-delimited list of integers. In that time, I have learned two foreign languages, because that was easier than learning regular expressions.īut it has all come to naught, I’m afraid.NET has great support for regular expressions, and it’s hard to do input validation without them. Occasionally, I’d break down and read an article on the subject, or buy yet another regular expressions book. I have spent the last ten years doing so deliberately, and with great effort. If you need extra regexes, just add a case to your enum.I have spent all of my life avoiding regular expressions. Not only, now all the patterns for our regular expressions are in one single place of our code.

#REGEX VALIDATOR CODE#

Let’s see now how readable our code is now: let isValid = “Username”.isValidWith(regexType. Writing clean code is our main goal often. Please remember to add small comments to every case of the enum in order to clarify everything. Line 40: our previous function with a small modification (see line 43).Wrapping it in a enum makes everything ultra readable.

Line 14: here I’ve created a private var pattern: String that returns the regex code.With this little variable, we are ready for everything. It’s common to have different string limits for a textual input in an app. Lines 8–9: I’ve used an associated value in my enums in order to give more flexibility to the rule.Line 5: I’ve created a none rule… just in case, you never know.Take a look at this article for this technique. Line 4: I’ve created a nested type inside Foundation String.Let’s build a whole manager inside the String Extension:Īs you can see I’ve created some examples to show you this approach. Luckily Swift gives us a pretty clean solution… we can use enum cases! If the answer is yes… well, you do not need this article and I’m sorry to say that you have wasted three minutes of your life 😁 … do not read anymore 😉. The second issue is readability… can you tell me what is this regex for? let isValid = “Username”.isValidWith(regex: #”^(?:||(?:|))$”#) What if you validate a user name in seven points of your app and the Business Department decides to change the validation rule? Maybe allowing blank spaces now? I assure you that you will not change the regex in all seven places and you will and up with a bug… maybe spotted a month later in production. If you write the regex pattern every time you need it you will eventually have problems and a so-called technical debt. If you are working on a big project, you will need to perform the same validation over and over in different sections. This solution is pretty nice but I see two issues here. It could be enough but we still have room for improvements. Wow! Much clearer and much more readable! Let’s take a look at our calling function now: let isValid = “UserName”.isValidWith(regex: #”^+$”#) Validate the text with the regex finding if there is an firstMatch in it.Ī first simplistic solution would be to create a function for the test:.

Create an NSRange with the string text, you want to validate… you could even validate just a section of your input text, hence the range.

Create an NSRegularExpression object with the regex pattern you want to apply.

The Foundation the framework comes with a bunch of methods to deal with regexes, so validating a text is really easy.

#REGEX VALIDATOR HOW TO#

If you want to learn how to create a regex, take a look at one of my latest articles where I showed you a really handy online tool. It is a technique developed in theoretical computer scienceand formal language theory.īasically, it’s a string with its own rules given to functions apt to analyze an input text and check if it matches the rules stated in the regex itself. Usually such patterns are used by string-searching algorithms for “find” or “find and replace” operations on strings, or for input validation.

Let’s start with some definitions taken from Wikipedia:Ī regular expression (shortened as regex or regexp also referred to as rational expression) is a sequence of characters that specifies a search pattern in text.

Regex validator