BitcartCC SDK Events System

Introduction

To be able to listen for incoming payments, transactions, new blocks or more, you should use events system.

In SDK, each event may have one handler.

One handler may handle multiple events at once

Using event system requires wallet.

Event handler signature is the following:

def handler(event, arg1, arg2):
    pass # process event

Where event is the only required argument everywhere.

Depending on the event being handled, it may provide additional arguments. All arguments must be named exactly as event is specifying.

If using event system from APIManager, then additional required argument instance is passed:

def handler(instance, event, arg1, arg2):
    pass # process event

Also, async handlers are supported too, like so:

async def handler(event, arg1, arg2):
    pass # process event, you can await here

Registering event handlers

To register an event handler, use on decorator:

@coin.on("event")
def handler(event, arg1, arg2):
    pass

You can also register a handler for multiple events, then you should mark all arguments, except for event and instance (if provided) optional, like so:

@coin.on(["event1", "event2"])
def handler(event, arg1=None, arg2=None, arg3=None):
    pass # event argument can be used to get what event is currently being processed

Or you can use add_event_handler method instead:

def handler(event, arg1, arg2):
    pass

coin.add_event_handler("event", handler)

They work identically.

Events list

new_block

Called when a new block is mined

Additional data:

• height (int): height of this block

new_transaction

Called when a new transaction on this wallet has appeared

Additional data:

• tx (str): tx hash of this transaction

new_payment

Called when status of payment request has changed. (See get_request/add_request)

Additional data:

• address (str): address related to this payment request

• status (int): new status code

• status_str (str): string version of new status code

Listening for updates

To receive updates, you should use one of the available event delivery methods: polling or websocket

Polling

Polling is good for quick testing, but not very good for production.

In this method SDK calls get_updates daemon method constantly, processing any new updates received.

To use it, run:

coin.poll_updates()

It will start an infinite loop.

Websocket

Websocket is a bit harder to set up sometimes, but works better.

Instead of constantly calling daemon method to get updates, daemon will send updates when they are available via an estabilished connection.

That way, you don’t need to know your URL, you should only know daemon URL, and a channel between SDK and daemon will be set up.

To use it, run:

coin.start_websocket()

It will connect to your daemon’s /ws endpoint, with auto-reconnecting in case of unexpected websocket close.

There may be unlimited number of websockets per wallet or not.

Under the hood, if using APIManager, daemon will send all it’s updates to SDK, and SDK will filter only the one you need.

If using coin object, daemon will only send updates about this wallet.

Manual updates processing

If you need complete control over updates delivery, you can pass updates to coin’s method directly:

coin.process_updates(updates_list)

Where updates_list is a list of dictionaries.

Each dictionary must contain event key, and additional keys for data required for this event.

Processing updates for multiple wallets/currencies

If you need to process updates for multiple wallets/currencies, take a look at APIManager documentation