title: NSExtension - Share - Limit type only to video or only to pictures
body: <p>I have an extension in my app that allows users to pick pictures or video of their 'Photos/Pictures' app to publish in my app.</p>
  
  <p>I limit the number of pictures to 20 and the limit of videos to 1 by doing the following :
  <a href="https://i.stack.imgur.com/gXNwO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gXNwO.png" alt="enter image description here"></a></p>
  
  <p>However, I want my users to select multiple pictures <strong>or</strong> only one video, which is not possible with this configuration.</p>
  
  <p>I have read this post: <a href="https://stackoverflow.com/questions/32265065/nsextension-share-extension-limit-photos-count/40742849#40742849">NSExtension Share Extension limit Photos count</a></p>
  
  <p>They explain that I can do a custom validation rule but I have no idea how to write it. Is there any other Activation parameter or can someone help with writing the rule?</p>
  
  <p>Thanks in advance!</p>