title: How to fix Cannot convert value of type ... to expected argument type inout _
body: <p>I have this simple Swift3 code where if complains about <code>[Channel]</code>:</p>
  
  <pre><code>        var channels = [Channel]()
          ....
  
          for (_, json) in json["entities"] {
              let channel = Channel(json: json)
              self.channels += [channel]
                   ^ Cannot convert value of type [Channel] to expected argument type inout _
          }
  </code></pre>
  
  <p>This is the channel class:</p>
  
  <pre><code>class Channel {
  
      var uuid: String
      var title: String?
      var isPublic: Bool
  
      init(uuid: String) {
          self.uuid = uuid
          self.title = ""
          self.isPublic = false
      }
  
      init?(json: JSON) {
          self.uuid = json["uuid"].stringValue
          self.title = json["title"].stringValue
          self.isPublic = json["public"].boolValue
      }
  }
  </code></pre>
  
  <p>Some postings indicate the message may be related to closures but I can't see a closure here.</p>
  
  <p>How to fix this error in a simple for loop?</p>