UITextField 正则表达式 匹配

注：设置（UITextField＊）的 delegate

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(Nsstring *)string

{

NSLog(@"%s",__FUNCTION__);

Nsstring *result = [textField.text stringByReplacingCharactersInRange:range withString:string];

if ([result length] == 0) return YES;

Nsstring *regex = @"^[a-zA-Z0-9_]{0,20}$";

nspredicate *prd = [nspredicate predicateWithFormat:@"SELF MATCHES %@",regex];

return [prd evaluateWithObject:result];

}