/// <summary>
/// Initializes a new instance of the <see cref="StrongMessageSubscription{TMessage}" /> class.
/// </summary>
/// <param name="subscriptionToken">The subscription token.</param>
/// <param name="deliveryAction">The delivery action.</param>
/// <param name="messageFilter">The message filter.</param>
/// <exception cref="ArgumentNullException">subscriptionToken
/// or
/// deliveryAction
/// or
/// messageFilter.</exception>
public StrongMessageSubscription(
MessageHubSubscriptionToken subscriptionToken,
Action <TMessage> deliveryAction,
Func <TMessage, bool> messageFilter)
{
SubscriptionToken = subscriptionToken ?? throw new ArgumentNullException(nameof(subscriptionToken));
_deliveryAction = deliveryAction;
_messageFilter = messageFilter;
}
/// <summary>
/// Initializes a new instance of the <see cref="WeakMessageSubscription{TMessage}" /> class.
/// </summary>
/// <param name="subscriptionToken">The subscription token.</param>
/// <param name="deliveryAction">The delivery action.</param>
/// <param name="messageFilter">The message filter.</param>
/// <exception cref="ArgumentNullException">subscriptionToken
/// or
/// deliveryAction
/// or
/// messageFilter.</exception>
public WeakMessageSubscription(
MessageHubSubscriptionToken subscriptionToken,
Action <TMessage> deliveryAction,
Func <TMessage, bool> messageFilter)
{
SubscriptionToken = subscriptionToken ?? throw new ArgumentNullException(nameof(subscriptionToken));
_deliveryAction = new WeakReference(deliveryAction);
_messageFilter = new WeakReference(messageFilter);
}
/// <summary>
/// Subscribe to a message type with the given destination and delivery action with the given filter.
/// Messages will be delivered via the specified proxy.
/// All references are held with WeakReferences
/// Only messages that "pass" the filter will be delivered.
/// </summary>
/// <typeparam name="TMessage">Type of message.</typeparam>
/// <param name="deliveryAction">Action to invoke when message is delivered.</param>
/// <param name="messageFilter">The message filter.</param>
/// <param name="useStrongReferences">Use strong references to destination and deliveryAction.</param>
/// <param name="proxy">Proxy to use when delivering the messages.</param>
/// <returns>
/// MessageSubscription used to unsubscribing.
/// </returns>
public MessageHubSubscriptionToken Subscribe <TMessage>(
Action <TMessage> deliveryAction,
Func <TMessage, bool> messageFilter,
bool useStrongReferences = true,
IMessageHubProxy?proxy = null)
where TMessage : class, IMessageHubMessage
{
if (deliveryAction == null)
{
throw new ArgumentNullException(nameof(deliveryAction));
}
if (messageFilter == null)
{
throw new ArgumentNullException(nameof(messageFilter));
}
lock (_subscriptionsPadlock)
{
if (!_subscriptions.TryGetValue(typeof(TMessage), out var currentSubscriptions))
{
currentSubscriptions = new List <SubscriptionItem>();
_subscriptions[typeof(TMessage)] = currentSubscriptions;
}
var subscriptionToken = new MessageHubSubscriptionToken(this, typeof(TMessage));
IMessageHubSubscription subscription;
if (useStrongReferences)
{
subscription = new StrongMessageSubscription <TMessage>(
subscriptionToken,
deliveryAction,
messageFilter);
}
else
{
subscription = new WeakMessageSubscription <TMessage>(
subscriptionToken,
deliveryAction,
messageFilter);
}
currentSubscriptions.Add(new SubscriptionItem(proxy ?? MessageHubDefaultProxy.Instance, subscription));
return(subscriptionToken);
}
}
/// <inheritdoc />
public void Unsubscribe <TMessage>(MessageHubSubscriptionToken subscriptionToken)
where TMessage : class, IMessageHubMessage
{
if (subscriptionToken == null)
{
throw new ArgumentNullException(nameof(subscriptionToken));
}
lock (_subscriptionsPadlock)
{
if (!_subscriptions.TryGetValue(typeof(TMessage), out var currentSubscriptions))
{
return;
}
var currentlySubscribed = currentSubscriptions
.Where(sub => ReferenceEquals(sub.Subscription.SubscriptionToken, subscriptionToken))
.ToList();
currentlySubscribed.ForEach(sub => currentSubscriptions.Remove(sub));
}
}
