title: filter dictionary of type [String: [object]] for specific key in object arrays
body: <p>I'm showing users a tableview that looks like the contacts view in the sense that the data source is a dictionary of type [String: [User]] and so I'm showing section headers with the first letter of the Users name.</p>
  
  <p>Now, I want to allow them to search by the users first name... but I can't get this to work.</p>
  
  <p>These are the dictionaries... the friends will hold data like this <code>["A" :[Users whose first name start with an A]]</code> and so on</p>
  
  <pre><code>var friends = [String: [User]]()
  var filteredFriends = [String: [User]]()
  </code></pre>
  
  <p>This is my filtering code with <code>searchText</code> being the first name I want to search by</p>
  
  <pre><code>self.filteredFriends = self.friends.filter{friend in
  return friend.firstName.lowercased().contains(searchText)}
  </code></pre>
  
  <p>What I want to do is make <code>filteredFriends</code> have all of the values of <code>friends</code> whose users first names start with the text.</p>
  
  <p>How do I make this work with a dictionary like mine?</p>
  
  <p>Thanks</p>
  
  <p>More Info:</p>
  
  <pre><code> Class User {
       var firstName: String?
  
       init(name: String){
          self.firstName = name
       }
   }
  </code></pre>
  
  <p>Sample scenario:</p>
  
  <pre><code>friends = ["A" : [User(name: "Anthony), User(name: "Arnold")], "B" : [User(name: "Barry")]]
  filteredFriends = friends
  
  searchText = "an"
  </code></pre>
  
  <p>Desired filteredFriends (end result) = <code>["A" : [User(name: "Anthony)]]</code></p>