text field 限制只输入字母和数字

1. - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string // return NO to not change text
   
2. {
   
3. //判断是否超过 ACCOUNT_MAX_CHARS 个字符,注意要判断当string.leng>0
   
4. //的情况才行，如果是删除的时候，string.length==0
   
5. int length = textField.text.length;
   
6. if (length >= ACCOUNT_MAX_CHARS && string.length >0)
   
7. {
   
8. return NO;
   
9. }
   
10. 
    
11. 
    
12. NSCharacterSet *cs;
    
13. cs = [[NSCharacterSet characterSetWithCharactersInString:kAlphaNum] invertedSet];
    
14. NSString *filtered =
    
15. [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    
16. BOOL basic = [string isEqualToString:filtered];
    
17. return basic;
    
18. }