Added weak self references to heartbeat

Sources/SwiftPhoenixClient/HeartbeatTimer.swift

@@ -78,7 +78,9 @@ class HeartbeatTimer {
   }
 
   func start(eventHandler: @escaping () -> Void) {
-    queue.sync {
+    queue.sync { [weak self] in
+      guard let self = self else { return }
+
       // Create a new DispatchSourceTimer, passing the event handler
       let timer = DispatchSource.makeTimerSource(flags: [], queue: queue)
       timer.setEventHandler(handler: eventHandler)
@@ -98,7 +100,9 @@ class HeartbeatTimer {
 
   func stop() {
     // Must be queued synchronously to prevent threading issues.
-    queue.sync {
+    queue.sync { [weak self] in
+      guard let self = self else { return }
+
       // DispatchSourceTimer will automatically cancel when released
       temporaryTimer = nil
       temporaryEventHandler = nil

Sources/SwiftPhoenixClient/PhoenixTransport.swift

@@ -190,6 +190,9 @@ open class URLSessionTransport: NSObject, PhoenixTransport, URLSessionWebSocketD
     super.init()
   }
 
+  deinit {
+    self.delegate = nil
+  }
 
 
   // MARK: - Transport
@@ -274,24 +277,26 @@ open class URLSessionTransport: NSObject, PhoenixTransport, URLSessionWebSocketD
   // MARK: - Private
   private func receive() {
     self.task?.receive { [weak self] result in
+      guard let self = self else { return }
+
       switch result {
       case .success(let message):
         switch message {
         case .data:
           print("Data received. This method is unsupported by the Client")
         case .string(let text):
-          self?.delegate?.onMessage(message: text)
+          self.delegate?.onMessage(message: text)
         default:
           fatalError("Unknown result was received. [\(result)]")
         }
 
         // Since `.receive()` is only good for a single message, it must
         // be called again after a message is received in order to
         // received the next message.
-        self?.receive()
+        self.receive()
       case .failure(let error):
         print("Error when receiving \(error)")
-        self?.abnormalErrorReceived(error, response: nil)
+        self.abnormalErrorReceived(error, response: nil)
       }
     }
   }

Sources/SwiftPhoenixClient/Socket.swift

@@ -238,6 +238,10 @@ public class Socket: PhoenixTransportDelegate {
   public var isConnected: Bool {
     return self.connectionState == .open
   }
+
+  public var isConnecting: Bool {
+    return self.connectionState == .connecting
+  }
 
   /// - return: The state of the connect. [.connecting, .open, .closing, .closed]
   public var connectionState: PhoenixTransportReadyState {
@@ -248,8 +252,8 @@ public class Socket: PhoenixTransportDelegate {
   /// will be sent through the connection. If the Socket is already connected,
   /// then this call will be ignored.
   public func connect() {
-    // Do not attempt to reconnect if the socket is currently connected
-    guard !isConnected else { return }
+    // Do not attempt to reconnect if the socket is currently connected or in the process of connecting
+    guard !isConnected && !isConnecting else { return }
 
     // Reset the close status when attempting to connect
     self.closeStatus = .unknown