Regular Expression

In theoretical computer science and formal language theory, a regular expression (sometimes called a rational expression) is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. “find and replace”-like operations. The concept arose in the 1950s, when the American mathematician Stephen Kleene formalized the description of a regular language, and came into common use with the Unix text processing utilities ed, an editor, and grep, a filter.

“^one”
“a dog$”
“^apple$”
“banana”
“ab”
“ab+”
“ab?”
“a?b+$”
“ab{4}”
“ab{1,}”
“ab{3,4}”
“a|b”
“(a|bcd)ef”
“(a|b)c”
“[ab]”
“[a-d]”
“^[a-zA-Z]”
“[0-9]a”
“[a-zA-Z0-9]$”
“a.[a-z]”
“^.{5}$”
“(.)\1”
“10{1,2}”
“0{3,}”
“@[^a-zA-Z]4@”
“\d”
“\D”
“\w”
“\W”

@”^\d+$”

 - (BOOL)validateNumber:(NSString *)textString {
     NSString *number = @"^[0-9]+$";
     NSPredicate *numberPre = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", number];
     return [numberPre evaluateWithObject:textString];
 }

 - (void)viewDidLoad {
     [super viewDidLoad];

     NSString *searchText = @"you want to match";

     NSString *searchText = @"rangeOfString";
     NSRange range = [searchText rangeOfString:@"^[0-9]+$" options:NSRegularExpressionSearch];
     if (range.location != NSNotFound) {
        NSLog(@"range ：%@", [searchText substringWithRange:range]);
     }

     NSError *error = NULL;
     NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"^[0-9]+$" options:NSRegularExpressionCaseInsensitive error:&error];
     NSTextCheckingResult *result = [regex firstMatchInString:searchText options:0 range:NSMakeRange(0, [searchText length])];
     if (result) {
         NSLog(@"%@", [searchText substringWithRange:result.range]);
     }
 }

Refer to: http://www.admin10000.com/document/5944.html
Learn more: http://www.cocoachina.com/programmer/20160513/16243.html