# Example - Get Random Number

The `GetRandomNumberExample` contract is an example of how to use the `GeneralRandcastConsumerBase` to request and consume randomness of type `Randomness`.

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {
    GeneralRandcastConsumerBase,
    BasicRandcastConsumerBase
} from "randcast-user-contract/user/GeneralRandcastConsumerBase.sol";

contract GetRandomNumberExample is GeneralRandcastConsumerBase {
    /* requestId -> randomness */
    mapping(bytes32 => uint256) public randomResults;
    uint256[] public randomnessResults;

    constructor(address adapter) BasicRandcastConsumerBase(adapter) {}

    /**
     * Requests randomness
     */
    function getRandomNumber() external returns (bytes32) {
        bytes memory params;
        return requestRandomness(RequestType.Randomness, params);
    }

    /**
     * Callback function used by Randcast Adapter
     */
    function fulfillRandomness(bytes32 requestId, uint256 randomness) internal override {
        randomResults[requestId] = randomness;
        randomnessResults.push(randomness);
    }

    function lengthOfRandomnessResults() public view returns (uint256) {
        return randomnessResults.length;
    }

    function lastRandomnessResult() public view returns (uint256) {
        return randomnessResults[randomnessResults.length - 1];
    }
}
```

Here's a step-by-step explanation of the `GetRandomNumberExample` contract:

1. Inherit the `GeneralRandcastConsumerBase` contract:

```solidity
contract GetRandomNumberExample is GeneralRandcastConsumerBase { ... }
```

2. Define a mapping `randomResults` to store randomness associated with each request ID:

```solidity
mapping(bytes32 => uint256) public randomResults;
```

3. Define an array `randomnessResults` to store all received randomness values:

```solidity
uint256[] public randomnessResults;
```

4. Implement the constructor to initialize the `adapter` address from the `GeneralRandcastConsumerBase` contract:

```solidity
constructor(address adapter) BasicRandcastConsumerBase(adapter) {}
```

5. Provide the `getRandomNumber()` function to request randomness:

```solidity
function getRandomNumber() external returns (bytes32) {
    bytes memory params;
    return requestRandomness(RequestType.Randomness, params);
}
```

This function calls the `requestRandomness()` function from the `GeneralRandcastConsumerBase` contract, which sends the randomness request to the `adapter`.

6. Override the `fulfillRandomness()` callback function:

```solidity
function fulfillRandomness(bytes32 requestId, uint256 randomness) internal override {
    randomResults[requestId] = randomness;
    randomnessResults.push(randomness);
}
```

When the `adapter` fulfills the randomness request, this function is called with the `requestId` and the generated `randomness`. The randomness value is stored in both the `randomResults` mapping and the `randomnessResults` array.

7. Provides helper functions to retrieve the length of the `randomnessResults` array and the last randomness result:

```solidity
function lengthOfRandomnessResults() public view returns (uint256) {
    return randomnessResults.length;
}

function lastRandomnessResult() public view returns (uint256) {
    return randomnessResults[randomnessResults.length - 1];
}
```

These functions allow users to query the length of the `randomnessResults` array and retrieve the last received randomness value.

Next, we will look at another example that uses the received random number as an entropy to throw a dice.


---

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