# EVMChainEvents

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEvents.ts:14](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEvents.ts#L14)

Backend event listener with persisted polling cursor stored on filesystem.

## Extends

* [`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md)

## Constructors

### Constructor

```
new EVMChainEvents(

   directory, 

   chainInterface, 

   evmSwapContract, 

   evmSpvVaultContract, 

   pollIntervalSeconds?): EVMChainEvents;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEvents.ts:19](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEvents.ts#L19)

#### Parameters

| Parameter              | Type                                                                                                                               |
| ---------------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
| `directory`            | `string`                                                                                                                           |
| `chainInterface`       | [`EVMChainInterface`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainInterface.md)            |
| `evmSwapContract`      | [`EVMSwapContract`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMSwapContract.md)                |
| `evmSpvVaultContract`  | [`EVMSpvVaultContract`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMSpvVaultContract.md)<`any`> |
| `pollIntervalSeconds?` | `number`                                                                                                                           |

#### Returns

`EVMChainEvents`

#### Overrides

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`constructor`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#constructor)

## Methods

### init()

```
init(noAutomaticPoll?): Promise<void>;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEvents.ts:88](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEvents.ts#L88)

Initializes the chains event listener, by default this initiates a websocket events subscription or HTTP polling for new events.

#### Parameters

| Parameter          | Type      | Description                                                                                                                                                                                                                                                                                     |
| ------------------ | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `noAutomaticPoll?` | `boolean` | When this flag is passed the listener doesn't initiate the websocket events subscription or HTTP polling, instead it relies on the implementor calling the [ChainEvents.poll](https://docs.atomiq.exchange/sdk-reference/api/atomiq-sdk/src/interfaces/ChainEvents.md#poll) to fetch new events |

#### Returns

`Promise`<`void`>

#### Overrides

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`init`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#init)

***

### poll()

```
poll(lastState?): Promise<object[]>;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEventsBrowser.ts:433](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEventsBrowser.ts#L433)

Triggers a single poll on the events instance, usually ran automatically, but should be called manually when initiated with `noAutomaticPoll`=`true`

#### Parameters

| Parameter    | Type        | Description                           |
| ------------ | ----------- | ------------------------------------- |
| `lastState?` | `object`\[] | The current state of the chain events |

#### Returns

`Promise`<`object`\[]>

The new state that should be saved, persisted and passed to the subsequent `poll()` call

#### Inherited from

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`poll`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#poll)

***

### registerListener()

```
registerListener(cbk): void;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEventsBrowser.ts:646](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEventsBrowser.ts#L646)

Registers a new listener to listen for on-chain events

#### Parameters

| Parameter | Type                                                                                                                         | Description |
| --------- | ---------------------------------------------------------------------------------------------------------------------------- | ----------- |
| `cbk`     | `EventListener`<[`EVMSwapData`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMSwapData.md)> |             |

#### Returns

`void`

#### Inherited from

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`registerListener`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#registerlistener)

***

### stop()

```
stop(): Promise<void>;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEventsBrowser.ts:631](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEventsBrowser.ts#L631)

Stops the event listener's polling and websocket subscription

#### Returns

`Promise`<`void`>

#### Inherited from

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`stop`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#stop)

***

### unregisterListener()

```
unregisterListener(cbk): boolean;
```

Defined in: [atomiq-chain-evm/src/evm/events/EVMChainEventsBrowser.ts:653](https://github.com/atomiqlabs/atomiq-chain-evm/blob/98ca6f16fbfb37e521f8c27b4f942642fe00c2ee/src/evm/events/EVMChainEventsBrowser.ts#L653)

Unregisters a previously registered events listener, returning `true` if success, `false` if failed

#### Parameters

| Parameter | Type                                                                                                                         | Description |
| --------- | ---------------------------------------------------------------------------------------------------------------------------- | ----------- |
| `cbk`     | `EventListener`<[`EVMSwapData`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMSwapData.md)> |             |

#### Returns

`boolean`

#### Inherited from

[`EVMChainEventsBrowser`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md).[`unregisterListener`](https://docs.atomiq.exchange/sdk-reference/api/atomiq-chain-evm/src/classes/EVMChainEventsBrowser.md#unregisterlistener)