iOS 限制输入身份证号

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

if (self.isIdentityNumber) {

NSMutableString *str = [NSMutableString stringWithFormat:@"%@",textField.text];

[str replaceCharactersInRange:range withString:string];

NSString *regex = @"[A-Za-z0-9]{0,18}";

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];

BOOL isValid = [predicate evaluateWithObject:str];

return isValid;

}

return YES;

}