title: Use of unresolved identifier FIRDatabase when using Firebase
body: <p>I am trying to use the Firebase database. I was watching a tutorial on how to use Firebase and wrote this line of code, <code>FIRDatabase.database().reference()</code>. Then I got an error saying, Use of unresolved identifier FIRDatabase. I don't know what is wrong I imported Firebase and FirebaseDatabase.</p>
  
  <p>My Podfile</p>
  
  <pre><code># Uncomment the next line to define a global platform for your project
  platform :ios, '10.2'
  
  target 'FirebaseDatabase' do
  # Comment the next line if you're not using Swift and don't want to use dynamic frameworks
  use_frameworks!
  
  # Pods for FirebaseDatabase
  
  pod 'Firebase'
  pod 'Firebase/Core'
  pod 'Firebase/Database'
  
  end
  </code></pre>