title: What is the right apporach to get data from Firebase? (on demand or everything at once))
body: <p>I am setting up a friendsystem in my app.
  For now, if I am in the ViewController with the list of friends, I only fetch their userdata, once it`s clicked on their username.
  I am now wondering if it is better to already load all data of the listed friends, in the VC where just the list is displayed.
  So that way, I can simply pass the userData-Array to next VC that shows their details, instead of loading it in the profile-VC.</p>
  <p>What are the pros and cons here?</p>