How do I separate strings like this?

Question

I get an NSString containing different emails concatenated together like

def_ghi@hotmail.com_abc_1@me.com

Each email is separated by an underscore.The problem is if I try to separate the string using the underscore character it would also subdivide a single e-mail address as an underscore character can also come in within a single e-mail. What I've tried gives me this result

def

ghi@hotmail.com

abc

1@me.com

Here is my code

NSString *string = //The string I am receiving.
NSArray *chunks = [string componentsSeparatedByString: @"_"];

Please help me.

EDIT: I asked a senior and he told me that I should first search the string for "@" character.When I find this,then I search for an "_" and replace it if it exists.As the first underscore after "@" is the separator.I should then start from this location and again repeat the previous step.I do this till the string ends.Please somebody help me with this.

You can't do this. You either need a delimiter that can't be part of the values or you must escape the delimiter character if it appears in a value. Otherwise there is no way to know how to properly split the string. — rmaddy, May 01 '13 at 04:56
I asked a senior and he told me that I should first search the string for "@" character.When I find this,then I search for an "_" and replace it if it exists.As the first underscore after "@" is the separator.I should then start from this location and again repeat the previous step.I do this till the string ends. — Jpk, May 01 '13 at 05:01
OK but I don't get why this is being made harder than it should. It would make so much more sense for everyone if the delimiter was changed to a character that can't appear in a valid email address. — rmaddy, May 01 '13 at 05:05

Thilina Chamath Hewagama · Accepted Answer · 2013-05-01T05:35:32.790

3

Solution using regular expressions,

NSString *yourString = @"def_ghi@hotmail.com_abc_1@me.com";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
                              regularExpressionWithPattern:@"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}"
                              options:NSRegularExpressionCaseInsensitive
                              error:&error];
[regex enumerateMatchesInString:yourString options:0 range:NSMakeRange(0, [yourString length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){

    // detect email addresses
    NSString *email = [yourString substringWithRange:match.range];

    //this part remove the '_' between email addresses
    if(match.range.location != 0){
        if([email characterAtIndex:0]=='_'){
            email = [email substringFromIndex:1];
        }
    }

    //print the email address
    NSLog(@"%@",email);

}];

EDIT: how to collect them,

declare a variable like this,

@property(nonatomic, strong) NSMutableArray *emailsArray;



 _emailsArray = [[NSMutableArray alloc] init];

NSString *yourString = @"def_ghi@hotmail.com_abc_1@me.com";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
                              regularExpressionWithPattern:@"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}"
                              options:NSRegularExpressionCaseInsensitive
                              error:&error];
[regex enumerateMatchesInString:yourString options:0 range:NSMakeRange(0, [yourString length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){

    // detect email addresses
    NSString *email = [yourString substringWithRange:match.range];

    //this part remove the '_' between email addresses
    if(match.range.location != 0){
        if([email characterAtIndex:0]=='_'){
            email = [email substringFromIndex:1];
        }
    }

    //print the email address
    NSLog(@"%@",email);
    [self.emailsArray addObject:email];
}];


NSLog(@"%@",self.emailsArray);

edited May 01 '13 at 05:35

answered May 01 '13 at 05:10

Thilina Chamath Hewagama

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@Thilina How do I add the check about the underscore in between the emails? Please edit your code .I don't understand regular expressions. – Jpk May 01 '13 at 05:20
@Jimmy Johnny, I changed the code and I added that part as well. Just copy the code and run it. cheers – Thilina Chamath Hewagama May 01 '13 at 05:21
@ThilinaHewagama That's not good advice. It is important that the OP understands the answer, not just blindly copies and uses it. – rmaddy May 01 '13 at 05:23
1

@rmaddy, i just ask him to run it and see the result first. then he knows that works. then I'm going to explain that. wait and see – Thilina Chamath Hewagama May 01 '13 at 05:24
@ThilinaHewagama Chose you as best answer.There is one last thing.How do I assign this email to my own NSString which I am returning? When I try to assign it,it says "variable is not assignable,missing block type specifier – Jpk May 01 '13 at 05:27
@ThilinaHewagama Fair enough. BTW - your regular expression may not be sufficient. The part before the `@` sign is supposed to be case sensitive and the part after isn't. Also, the part before the `@` sign is officially allowed to have many more characters than you have in your regular expression. – rmaddy May 01 '13 at 05:30
@Jimmy, to collect them, I added a NSMutableArray *emailsArray, and then inside the code you can add those email addresses to the mutable array. I added that part to the answer. – Thilina Chamath Hewagama May 01 '13 at 05:34
My function is a static function.It is returning an NSString.I am returning after replacing the parameter with the updated value.Please help me with this as I don't understand about blocks. – Jpk May 01 '13 at 05:37
@Jimmy,ok what do you want to return from your static method ? – Thilina Chamath Hewagama May 01 '13 at 05:38
I want to return an NSString – Jpk May 01 '13 at 05:49
1

This won't work. http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address – maroux May 01 '13 at 05:53
String of what ? do you want to return the first email address, or 2nd email address or number of email addresses or what ? – Thilina Chamath Hewagama May 01 '13 at 05:54

Monolo · Answer 2 · 2013-05-01T05:44:20.663

1

There are many good answers here on how to re-construct the original list of mail addresses from that somewhat messy string you found yourself with.

I would propose an NSScanner based solution, it seems to be well suited:

NSString *messyString = @"def_ghi@hotmail.com_abc_1@me.com";

NSScanner *mailScanner = [NSScanner scannerWithString:messyString];

NSMutableArray *mailAddresses = [NSMutableArray array];

while (YES) {

    NSString *recipientName;
    NSString *serverName;
    BOOL found = [mailScanner scanUpToString:@"@" intoString:&recipientName];
    found |= [mailScanner scanUpToString:@"_" intoString:&serverName];
    if ( !found ) break;

    [mailAddresses addObject:[recipientName stringByAppendingString:serverName]];

    // Consume the delimiting underscore
    found = [mailScanner scanString:@"_" intoString:nil];
    if ( !found ) break;
}

edited May 01 '13 at 05:44

answered May 01 '13 at 05:31

Monolo

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I always forget about `NSScanner` for some reason. This is much simpler than my code. Two typos though - 1) It's `found |=`. 2) No need for the semicolon at the end of the `while` block. – rmaddy May 01 '13 at 05:36
Thanks for using cocoa-sheet in few questions :) – Anoop Vaidya May 01 '13 at 06:28
now I wonder `cocoa-sheet` is good name of `nswindow-sheet` or even `NSSheet` which actually doesn't exist. But I hear from many noobs. – Anoop Vaidya May 01 '13 at 06:34

Anupdas · Answer 3 · 2013-05-01T05:17:41.310

Try

NSString *string = @"def_ghi@hotmail.com_abc_1@me.com";
NSArray *stringComponents = [string componentsSeparatedByString:@"_"];

NSMutableString *mutableString = [NSMutableString string];
NSMutableArray *emailIDs = [NSMutableArray array];
for (NSString *component in stringComponents) {
    if (!mutableString) {
        mutableString = [NSMutableString string];
    }
    [mutableString appendFormat:@"_%@",component];

    if ([component rangeOfString:@"@"].location != NSNotFound) {
        [emailIDs addObject:[mutableString substringFromIndex:1]];
        mutableString = nil;
    }
}

NSLog(@"%@",emailIDs);

score 0 · Answer 4 · answered May 01 '13 at 05:20

Given your requirements then something like this should work for you:

NSString *string = @"def_ghi@hotmail.com_abc_1@me.com";
NSMutableArray *addresses = [NSMutableArray array];
NSUInteger currentIndex = 0; // start from beginning
// Stop when we are past the end of the string
while (currentIndex < string.length) {
    // Find the next @ symbol
    NSRange atRange = [string rangeOfString:@"@" options:0 range:NSMakeRange(currentIndex, string.length - currentIndex)];
    if (atRange.location != NSNotFound) {
        // We found another @, not look for the first underscore after the @
        NSRange underRange = [string rangeOfString:@"_" options:0 range:NSMakeRange(atRange.location, string.length - atRange.location)];
        if (underRange.location != NSNotFound) {
            // We found an underscore after the @, extract the email address
            NSString *address = [string substringWithRange:NSMakeRange(currentIndex, underRange.location - currentIndex)];
            [addresses addObject:address];
            currentIndex = underRange.location + 1;
        } else {
            // No underscore so this must be the last address in the string
            NSString *address = [string substringFromIndex:currentIndex];
            [addresses addObject:address];
            currentIndex = string.length;
        }
    } else {
        // no more @ symbols
        currentIndex = string.length;
    }
}

NSLog(@"Addresses: %@", addresses);

How do I separate strings like this?

4 Answers4