UITextField文本内容显示alert

有两个UITextField，我想要检测UITextField，当满足两个UITextField都有文本内容时，显示alert，如果只有一个UITextField有文本内容时向下一步进行。

if([txt1.text length] > 0 && [txt2.text length]>0)
    {   
        UIAlertView * alert=[ [UIAlertView alloc]initWithTitle:@"Alert" message:@"TextFied Have an Text" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil, nil];

        [alert show];   
    }
else
   {
        //Go Forword
   }

执行 UITextField 代理：

- (void)textFieldDidEndEditing:(UITextField *)textField
{
    if ([textField1.text length] > 0 && [textField2.text length] > 0)
    {
        UIAlertView *alert = [ [UIAlertView alloc]initWithTitle:@"" message:@"Hello" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alert show];
    }
   else 
   {
                // go forward here.....
   }
}