UITextView和UITextField限制输入长度

UITextView要实现UITextViewDelegate协议:

 _descriptionTextView.delegate=self;

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    if ([text isEqualToString:@""] && range.length > 0) {
    // 删除字符肯定是安全的
    return YES;
    }
    if (textView.text.length - range.length + text.length > 1000) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"超出最大长度" message:nil delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
    [alert show];
    return NO;
    }
    return YES;
}

UITextField要实现UITextFieldDelegate协议:

 _exchangeTextField.delegate=self;

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (textField == self.exchangeTextField && textField.isFirstResponder) {
        NSString *toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];
           if ([toBeString length] > 8) {
               textField.text = [toBeString substringToIndex:8];
               UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"超出最大长度" message:nil delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
               [alert show];
               return NO;
           }
           return YES;
    }
     return YES;
   
}