Q:

Objective C: How to grab a number after a sub string from string

I have a lengthy string as below

Please plan to attend to provide upgrade to existing code
morning meeting to acoomdate bum team members
Meeting Number: 457 231 123

To join this meeting

go to http://domainname.com
enter password

Now i want to grab number after the text "Meeting Number"
i.e. 457 231 123
Any help please.
thanks
EDIT
Lets say i have a string 
NSString *myString = @"Please plan to attend to provide upgrade to existing code morning meeting to acoomdate bum team members  Meeting Number: 457 231 123 ----------------------------------------------------- to join this meeting ------------------------------------------------------  1. go to http://domainname.com 2. enter password"

A:

You want NSScanner. It's there specifically for this sort of thing.
NSScanner *scanner = [NSScanner scannerWithString:yourString];
NSString *prefix = @"Meeting number: ";
NSString *numbers;
[scanner scanUpToString:prefix intoString:NULL];
[scanner scanString:prefix intoString:NULL];
[scanner scanUpToCharactersFromSet:[NSCharacterSet newlineCharacterSet] intoString:&numbers];
// numbers now contains the numbers you want.

(This can be trivially adapted to find any number by doing scanUpToCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet] instead of the two lines with the prefix string.)

A:

You may use regular expressions to capture the numbers also (assuming that there is only numeric characters and spaces in the result, and there is always the "Meeting Number: " prefix):
NSString *text = @"Please plan to attend to provide upgrade to existing code\nmorning meeting to acoomdate bum team members\nMeeting Number: 457 231 123\nTo join this meeting\n\ngo to http://domainname.com\nenter password";
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"Meeting Number: ([0-9 ]+)" options:NSRegularExpressionCaseInsensitive error:&error];
NSArray *matches = [regex matchesInString:text
                                  options:0
                                    range:NSMakeRange(0, [text length])];
for (NSTextCheckingResult *match in matches) {
    NSRange matchRange = [match rangeAtIndex:1];
    NSString *result = [text substringWithRange:matchRange]; // Here is the result
}

this can be used to parse multiple inputs together since we have a loop here. If the requirements is just to parse one input, replace the code after the declaration of the regex with:
NSTextCheckingResult *match = [regex firstMatchInString:text
                                                options:0
                                                  range:NSMakeRange(0, [text length])];
if (match) {
    NSRange matchRange = [match rangeAtIndex:1];
    NSString *result = [text substringWithRange:matchRange];
}

