Use of OC Regular Expressions and OC Regular Expressions

Use of OC Regular Expressions and OC Regular Expressions

Generally, the use of regular expressions in OC is two steps.

1. Create a regular expression object

2. Use a regular expression to test the corresponding string

For example

NSString * checkString = @ "a34sd231"; // 1. create a regular expression. [0-9]: indicates the NSString * pattern = @ "[0-9]" set of characters from '0' to '9'. // 1.1 set the regular expression to the OC rule NSRegularExpression * regular = [[NSRegularExpression alloc] initWithPattern: pattern options: NSRegularExpressionCaseInsensitive error: nil]; // 2. use the rule test string to obtain the matching result NSArray * results = [regular matchesInString: checkString options: 0 range: NSMakeRange (0, checkString. length)]; NSLog (@ "% ld", results. count );

Obtain the print result. The number of characters analyzed from checkString is 5.

Therefore, we can draw a conclusion that the function of a regular expression is to mix multiple strings into one expression.

Here we can understand the meaning of the regular expression. Next we will introduce some common Regular Expression characters.

/* []: Find an internal character [a-zA-Z0-9] ==> stands for character or number \ d ==> stands for number {2 }: two {2, 4}: two to four //? + * ^ $ .? : Represents 0 or 1 +: represents at least 1 *: represents 0 or more ^: represents... $: indicates that... end.: any character except line breaks */
// Represents a number character
NSString * pattern = @ "\ d ";
// Two to five consecutive numbers
NSString * pattern = @ "\ d {2, 5 }";
// The regular expression of the qq account
NSString * pattern = @ "^ [1-9] \ d {4, 10 }";
// Regular Expression in phone number format
NSString * pattern = @ "^ (13 [0-9]) | (15 [3-5]) | (18 [07-9]) \ d {8} $"
// Regular Expression of the mailbox
NSString * pattern = @ "^. * @... + \. [a-zA-Z] {2, 4} $"

In this way, you can set a regular expression based on the matching rules to determine whether the string is of the correct type.

If there is a long string, you must match the expression, url, @ (CALL), or # topic #.

Multiple regular expressions are required for determination.

// The string NSString * str = @ "# today's news # [Laugh] http://asd.fdfs. 2ee/aas/1e @ sdf [test] # Are you sure # @ rain Li 23: @ Zhang San [Snoop] m123m "; // expression Regular Expression // \ u4e00-\ u9fa5 stands for the unicode Character NSString * emopattern = @ "\ [[a-zA-Z \ u4e00-\ u9fa5] + \] "; // @ regular expression NSString * atpattern = @ "@ [0-9a-zA-Z \ u4e00-\ u9fa5] + ";//#... # Regular Expression NSString * toppattern = @ "# [0-9a-zA-Z \ u4e00-\ u9fa5] + #"; // url Regular Expression NSString * urlpattern = @ "\ B ([\ w-] + ://? | Www [.]) [^ \ s () <>] + (?: \ ([\ W \ d] + \) | ([^ [: punct:] \ s] | /)))"; // set the general Regular Expression NSString * pattern = [NSString stringWithFormat: @ "% @ | % @ |%@|%@", emopattern, atpattern, toppattern, urlpattern]; // set the OC rule NSRegularExpression * regular = [[NSRegularExpression alloc] initWithPattern: pattern options: NSRegularExpressionCaseInsensitive error: nil] According to the regular expression; // obtain the matching result NSArray * results = [regular matchesInString: str options: 0 range: NSMakeRange (0, str. length)]; // NSLog (@ "% @", results); // traverses the result for (NSTextCheckingResult * result in results) {NSLog (@ "% @", NSStringFromRange (result. range), [str substringWithRange: result. range]);}

Obtain results

With the above demonstration, you can roughly write the regular expression used by the system method.