What is the current Parse email verification regex pattern? - ios

Question

I am currently using the PFUser method ' signUpInBackgroundWithBlock: ' to sign up my users, but constraints on my UX mean that i can't sign them up on the same ViewController, hence I'm trying to validate the email before calling that method on a PFUser Parse object.
The alternative is to send my users back to earlier view controllers if parse gives me an error back after method call (which I do not want to do)
I have found this Regex pattern, but this is quite an old answer and I know fancier domains have been out since are now out:
https://www.parse.com/questions/email-validation-rules-for-pfsignupviewcontroller

Answer 1

"The alternative is to send my users back to earlier view controllers if parse gives me an error back after method call (which I do not want to do)"
Note - Unfortunately, you simply won't be able to build parse apps unless you "send them back" like that. Unfortunately "it's that simple." Quite literally every single such "step" when dealing with Parse, you have to be able to "go back" in the sense you describe.
In answer to your question, as you probably know essentially THERE IS NO really good way to truly check if a string is an email, due to various problems with the nature of defining an email, and the fact that you simply don't actually want the full set of "really possible" email strings, for any app.
In practice the following category works well.
It's in use in many high volume production apps.
Note that NSPredicate is, I feel, the most natural, reliable way to do this in iOS.
-(BOOL)basicLocalEmailCheck
{
if ( self.length > 50 ) return NO;
// note, first if it ends with a dot and one letter - that is no good
// (the regex below from W3C does allow a final single-letter tld)
NSString *rx = #".*\\..$";
NSPredicate *emailTest = [NSPredicate
predicateWithFormat:#"SELF MATCHES %#", rx];
if ( [emailTest evaluateWithObject:self] ) return NO;
// here's the original from the W3C HTML5 spec....
// ^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+#[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$
// i made a modification,
// you can't have eg "localhost" with no .com,
// and note you have to escape one backslash for the string from the W3C
rx = #"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+#[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?){1,5}$";
emailTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", rx];
return [emailTest evaluateWithObject:self];
}
If you are a beginner and not familiar with categories, it's a good opportunity to use one.
Here are some typical real-world uses...particularly relating to Parse since you mention that.
-(IBAction)joinNow
{
[self.view endEditing:YES];
if ( [self _fieldBlank] )
{ [self woe:#"Please complete all fields."]; return; }
if ( ! [self.email.text basicLocalEmailCheck] )
{ [self woe:#"Please enter a valid email."]; return; }
if ( self.imageHasBeenSet == NO )
{ [self woe:#"Please add a picture."]; return; }
if ( self.password.text.length > 20 ||
self.firstname.text.length > 20 ||
self.surname.text.length > 20 )
{ [self woe:#"20 character limit for names and password."]; return; }
[self ageConfirmThenJoin];
}
-(IBAction)clickLogin:(id)sender
{
[self.view endEditing:YES];
[PFUser logOut];
if ( ! [self.loginEmail.text basicLocalEmailCheck] )
{
[UIAlertView ok:#"Please enter your email in the email field."];
[self begin];
return;
}
[APP huddie];
APP.hud.labelText = #"Logging in ...";
[PFAnalytics trackEvent:#"loginAttempt"];
[PFUser logInWithUsernameInBackground: [self.loginEmail.text lowercaseString]
password: self.loginPassword.text
block:^(PFUser* user, NSError* error)
{
[APP.hud hide:YES];
if (user) // Login successful
{
[PFAnalytics trackEvent:#"loginSuccess"];
[self isLoggedInCheckValid];
return;
}
else
{
// note, with Parse it SEEMS TO BE THE CASE that
// 100, no connection 101, bad user/pass
NSString *msg;
NSString *analyticsMsg = #"otherProblem";
if ( !error)
{
msg = #"Could not connect. Try again later...";
// seems unlikely/impossible this could happen
}
else
{
if ( [error code] == 101 )
{
msg = #"Incorrect email or password. Please try again.";
analyticsMsg = #"passwordWrong";
}
else
{
msg = #"Could not connect. Try again later.";
}
}
[PFAnalytics trackEvent:#"loginFailure"
dimensions:#{ #"reason":analyticsMsg }];
[UIAlertView ok:msg];
[self begin]; // not much else we can do
return;
}
}];
}

Answer 2

If you are after a regular expression, then you could take a look here and here for some solutions.
That being said, if you truly want to ensure that the user has provided you with a valid, active email account you should simply do some very basic validation (see it contains the # character for instance) and then simply send a mail with a link to activate the account.
The regular expressions linked to the answers provided aren't exactly user friendly. To add insult to injury, users can still provide you with bogus email addresses. It might also be the case where an edge case scenario email address fails the verification, thus according to your site the user won't be able to sign up.