# BlockProposer

Represents the entity that proposed a block. Can be the system itself or a validator identified by public key.

## Import

```ts
import { Proposer } from 'casper-js-sdk';
```

## Class

### `Proposer`

| Property | Type | Description |
|---|---|---|
| `isSystem` | `boolean` | Whether this is a system-level proposer |
| `publicKey?` | `PublicKey` | Validator's public key (absent for system proposers) |

#### Constructor

```ts
new Proposer(isSystem?: boolean, publicKey?: PublicKey)
```

#### Methods

```ts
proposer.isSystemProposer(): boolean
proposer.getPublicKey(): PublicKey            // throws if system
proposer.getPublicKeyOptional(): PublicKey | undefined
proposer.toJSON(): string
```

#### Static Methods

```ts
Proposer.fromString(src: string): Proposer
Proposer.fromJSON(json: string): Proposer
```

## Usage

```ts
import { RpcClient, HttpHandler } from 'casper-js-sdk';

const client = new RpcClient(new HttpHandler('http://node:7777/rpc'));
const { block } = await client.getLatestBlock();

const proposer = block.proposer;

if (proposer.isSystemProposer()) {
  console.log('System block');
} else {
  console.log('Proposed by:', proposer.getPublicKey().toHex());
}
```

## See Also

- [`Block`](/types/block) - Block type that contains a `Proposer`