• Unity SDK
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  • ContractEventSubscriber

ContractEventSubscriber

A class that contains methods for making real-time subscriptions for contracts' events.

Constructors:

Properties:

  • RequestHeaders — a dictionary of specific headers.

Events:

  • OnOpenHandler — fires when a connection to a node opens.
  • OnErrorHandler — fires when a connection fails.
  • OnCloseHandler — fires when a connection closes.

Public methods

  • Subscribe — subscribes to an event with the given parameters.
  • ListenForEvents — opens a connection to a node and starts listening to events.
  • Unsubscribe — unsubscribes from events by a subscription ID.
  • StopListen — closes a connection to a node.

Code example

using MirageSDK.Core.Infrastructure;
using MirageSDK.Data;
using MirageSDK.DTO;
using MirageSDK.Examples.ERC20Example;
using MirageSDK.Provider;
using MirageSDK.UseCases;
using Cysharp.Threading.Tasks;
using UnityEngine;
 
namespace MirageSDK.EventListenerExample
{
	public class EventListenerExample : UseCase
	{
		private IContractEventSubscriber _eventSubscriber;
		private IContractEventSubscription _subscription;
		private IEthHandler _eth;
		
		public override void ActivateUseCase()
		{
			base.ActivateUseCase();
			
 
			var mirageSDK = MirageSDKFactory.GetMirageSDKInstance("https://");
			_eth = mirageSDK.Eth;
 
			_eventSubscriber = mirageSDK.CreateSubscriber("wss://");
			_eventSubscriber.ListenForEvents().Forget();
			_eventSubscriber.OnOpenHandler += UniTask.Action(SubscribeWithRequest);
		}
 
		// If you know topic position then you can use EventFilterData
		public async UniTaskVoid SubscribeWithTopics()
		{
			var filters = new EventFilterData
			{
				FilterTopic2 = new object[] { await _eth.GetDefaultAccount() }
			};
 
			_subscription = await _eventSubscriber.Subscribe(
				filters,
				ERC20ContractInformation.ContractAddress, 
				(TransferEventDTO t) => ReceiveEvent(t)
			);
		}
		
		// If you know only topic name then you can use EventFilterRequest
		public async UniTaskVoid SubscribeWithRequest()
		{
			var filtersRequest = new EventFilterRequest<TransferEventDTO>();
			filtersRequest.AddTopic("To", await _eth.GetDefaultAccount());
 
			_subscription = await _eventSubscriber.Subscribe(
				filtersRequest,
				ERC20ContractInformation.ContractAddress, 
				ReceiveEvent
			);
		}
 
		private void ReceiveEvent(TransferEventDTO contractEvent)
		{
			Debug.Log($"{contractEvent.From} - {contractEvent.To} - {contractEvent.Value}");
		}
 
		public void Unsubscribe()
		{
			_eventSubscriber.Unsubscribe(_subscription.SubscriptionId).Forget();
		}
 
		public override void DeActivateUseCase()
		{
			base.DeActivateUseCase();
			_eventSubscriber.StopListen();
		}
	}
}

Constructor

Declaration

ContractEventSubscriber(string wsUrl)

Parameters:

  • wsUrl (string) — an RPC endpoint for the WebSockets connection.

Subscribe

Declaration

UniTask<IContractEventSubscription> Subscribe<TEventType>(EventFilterData evFilter, string contractAddress, Action<TEventType> handler) OR

UniTask<IContractEventSubscription> Subscribe<TEventType>(EventFilterRequest<TEventType> evFilter, string contractAddress, Action<TEventType> handler)

Parameters:

  • evFilter (data object) — an object containing request parameters.
  • contractAddress (string) — an address of the contract that emits events.
  • handler — an action that handles received events.

Returns

  • IContractEventSubscription — a subscription object.

Subscribes to events with specific request parameters. Use it only to subscribe for events emitted after a subscription start, the method doesn’t return past events.

To find out more info on events and subscriptions, have a look at Events and subscriptions.

Code example

var filtersRequest = new EventFilterRequest<TransferEventDTO>();
filtersRequest.AddTopic("To", await _eth.GetDefaultAccount());
 
var subscription = await _eventSubscriber.Subscribe(
	filtersRequest,
	"0x...", 
	contractEvent => Debug.Log($"{contractEvent.From} - {contractEvent.To} - {contractEvent.Value}")
);

The full code example lives here.

ListenForEvents

Declaration

UniTask ListenForEvents()

Connects to a given endpoint and starts listening for events.

Unsubscribe

Declaration

UniTask Unsubscribe(string subscriptionId)

Parameters:

  • subscriptionId — an identifier of a subscription.

Unsubscribes from the events with a given identifier.

Code example

var filtersRequest = new EventFilterRequest<TransferEventDTO>();
filtersRequest.AddTopic("To", await _eth.GetDefaultAccount());
 
var subscription = await _eventSubscriber.Subscribe(
	filtersRequest,
	"0x...", 
	contractEvent => Debug.Log($"{contractEvent.From} - {contractEvent.To} - {contractEvent.Value}")
);
 
await _eventSubscriber.Unsubscribe(subscription.SubscriptionId);

StopListen

Declaration

void StopListen()

Closes the WebSockets connection, unsubscribes from all subscriptions.

ContractAptos Integration