Events

Summary

The event pipeline allows developers to easily create real-time applications by letting them listen for important state changes and lifecycle events.

Wildcards

• An event name passed to any event emitter method can contain a wildcard (the *character). A wildcard may appear as foo/*, foo/bar/*, or simply *.

• * matches one sub-level.

e.g. price/* will trigger on both price/USD_ETH and price/MKR_USD but not price/MKR_USD/foo.

• ** matches all sub-levels.

e.g. price/** will trigger on price/USD_ETH, price/MKR_USD, and price/MKR_USD/foo.

Event Object

Triggered events will receive the object shown on the right.

• <event_type> - the name of the event

• <event_payload> - the new state data sent with the event

• <event_sequence_number> - a sequentially increasing index

• <latest_block_when_emitted> - the current block at the time of the emit

{
    type: <event_type>,
    payload: <event_payload>, /* if applicable */
    index: <event_sequence_number>,
    block: <latest_block_when_emitted>
}

Maker Object

Price

Event Name	Payload
price/ETH_USD	{ price }
price/MKR_USD	{ price }
price/WETH_PETH	{ ratio }

maker.on('price/ETH_USD', eventObj => {
    const { price } = eventObj.payload;
    console.log('ETH price changed to', price);
})

Web3

Event Name	Payload
web3/INITIALIZED	{ provider: { type, url } }
web3/CONNECTED	{ api, network, node }
web3/AUTHENTICATED	{ account }
web3/DEAUTHENTICATED	{ }
web3/DISCONNECTED	{ }

maker.on('web3/AUTHENTICATED', eventObj => {
    const { account } = eventObj.payload;
    console.log('web3 authenticated with account', account);
})

CDP Object

Event Name	Payload
COLLATERAL	{ USD, ETH }
DEBT	{ dai }

cdp.on('DEBT', eventObj => {
    const { dai } = eventObj.payload;
    console.log('Your cdp now has a dai debt of', dai);
})