Check that an email address is valid on iOS

Question

Possible Duplicate    Best practices for validating email address in Objective-C on iOS 2 0        I am developing an iPhone application where I need the user to give his email address at login   What is the best way to check if an email address is a valid email address

User · Answer

to validate the email string you will need to write a regular expression to check it is in the correct form. there are plenty out on the web but be carefull as some can exclude what are actually legal addresses.

essentially it will look something like this

^((?>[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+\x20*|"((?=[\x01-\x7f])[^"\\]|\\[\x01-\x7f])*"\x20*)*(?<angle><))?((?!\.)(?>\.?[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+)+|"((?=[\x01-\x7f])[^"\\]|\\[\x01-\x7f])*")@(((?!-)[a-zA-Z\d\-]+(?<!-)\.)+[a-zA-Z]{2,}|\[(((?(?<!\[)\.)(25[0-5]|2[0-4]\d|[01]?\d?\d)){4}|[a-zA-Z\d\-]*[a-zA-Z\d]:((?=[\x01-\x7f])[^\\\[\]]|\\[\x01-\x7f])+)\])(?(angle)>)$

Actually checking if the email exists and doesn't bounce would mean sending an email and seeing what the result was. i.e. it bounced or it didn't. However it might not bounce for several hours or not at all and still not be a "real" email address. There are a number of services out there which purport to do this for you and would probably be paid for by you and quite frankly why bother to see if it is real?

It is good to check the user has not misspelt their email else they could enter it incorrectly, not realise it and then get hacked of with you for not replying. However if someone wants to add a bum email address there would be nothing to stop them creating it on hotmail or yahoo (or many other places) to gain the same end.

So do the regular expression and validate the structure but forget about validating against a service.

User · Answer

Heres a good one with NSRegularExpression that s working for me    text rangeOfString              2     options NSRegularExpressionSearch  location    NSNotFound   You can insert whatever regex you want but I like being able to do it in one line

User · Answer

To check if a string variable contains a valid email address  the easiest way is to test it against a regular expression  There is a good discussion of various regex s and their trade-offs at regular-expressions info   Here is a relatively simple one that leans on the side of allowing some invalid addresses through    A-Z0-9    -    A-Z0-9 -     A-Z  2 6    How you can use regular expressions depends on the version of iOS you are using   iOS 4 x and Later  You can use NSRegularExpression  which allows you to compile and test against a regular expression directly   iOS 3 x  Does not include the NSRegularExpression class  but does include NSPredicate  which can match against regular expressions   NSString  emailRegex        NSPredicate  emailTest    NSPredicate predicateWithFormat   SELF MATCHES      emailRegex   BOOL isValid    emailTest evaluateWithObject checkString     Read a full article about this approach at cocoawithlove com   iOS 2 x  Does not include any regular expression matching in the Cocoa libraries  However  you can easily include RegexKit Lite in your project  which gives you access to the C-level regex APIs included on iOS 2 0

User · Answer

Good cocoa function   - BOOL  NSStringIsValidEmail  NSString   checkString      BOOL stricterFilter   NO     Discussion http   blog logichigh com 2010 09 02 validating-an-e-mail-address     NSString  stricterFilterString       A-Z0-9a-z      -     A-Za-z0-9-        A-Za-z  2 4        NSString  laxString           A-Za-z0-9-        A-Za-z  2  A-Za-z         NSString  emailRegex   stricterFilter   stricterFilterString   laxString     NSPredicate  emailTest    NSPredicate predicateWithFormat   SELF MATCHES      emailRegex      return  emailTest evaluateWithObject checkString       Discussion on Lax vs  Strict - http   blog logichigh com 2010 09 02 validating-an-e-mail-address   And because categories are just better  you could also add an interface    interface NSString  emailValidation     -  BOOL isValidEmail   end   Implement   implementation NSString  emailValidation  - BOOL isValidEmail     BOOL stricterFilter   NO     Discussion http   blog logichigh com 2010 09 02 validating-an-e-mail-address    NSString  stricterFilterString       A-Z0-9a-z      -     A-Za-z0-9-        A-Za-z  2 4       NSString  laxString           A-Za-z0-9-        A-Za-z  2  A-Za-z        NSString  emailRegex   stricterFilter   stricterFilterString   laxString    NSPredicate  emailTest    NSPredicate predicateWithFormat   SELF MATCHES      emailRegex     return  emailTest evaluateWithObject self      end   And then utilize   if    emailString email com  isValidEmail        True      if    InvalidEmail notreallyemailbecausenosuffix  isValidEmail        False

[objective-c] Check that an email address is valid on iOS

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