# Example - Shuffle an Array

The `GetShuffledArrayExample` is an example of how to use the `GeneralRandcastConsumerBase` to request and consume randomness of type `Shuffling` to request a shuffled array.

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

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

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

    constructor(address adapter) BasicRandcastConsumerBase(adapter) {}

    /**
     * Requests randomness
     */
    function getShuffledArray(uint32 upper) external returns (bytes32) {
        bytes memory params = abi.encode(upper);
        return requestRandomness(RequestType.Shuffling, params);
    }

    /**
     * Callback function used by Randcast Adapter
     */
    function fulfillShuffledArray(bytes32 requestId, uint256[] memory array) internal override {
        randomResults[requestId] = array;
        shuffleResults = array;
    }

    function lengthOfShuffleResults() public view returns (uint256) {
        return shuffleResults.length;
    }
}
```

Here's a breakdown of the `GetShuffledArrayExample` contract:

1. Imports the necessary contract:

```solidity
import "../GeneralRandcastConsumerBase.sol";
```

2. Inherits the imported contract:

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

3. Defines a mapping and an array to store the randomness results:

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

`randomResults` maps request IDs to the corresponding shuffled arrays received from the `adapter`. `shuffleResults` holds the latest shuffled array.

4. Initializes the contract with the `adapter` address:

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

5. Implements the `getShuffledArray()` function to request a shuffled array:

```solidity
function getShuffledArray(uint32 upper) external returns (bytes32) {
    bytes memory params = abi.encode(upper);
    return requestRandomness(RequestType.Shuffling, params);
}
```

The function takes an `upper` parameter to define the upper bound of the array elements (0 to `upper` - 1) and requests a shuffled array from the `adapter` using the `requestRandomness` function inherited from `GeneralRandcastConsumerBase`.

6. Overrides the `fulfillShuffledArray()` function to handle the shuffled array returned by the `adapter`:

```solidity
function fulfillShuffledArray(bytes32 requestId, uint256[] memory array) internal override {
    randomResults[requestId] = array;
    shuffleResults = array;
}
```

This function stores the shuffled array in the `randomResults` mapping and updates the `shuffleResults` array with the latest shuffled array.

7. Implements the `lengthOfShuffleResults()` function to return the length of the latest shuffled array:

```solidity
function lengthOfShuffleResults() public view returns (uint256) {
    return shuffleResults.length;
}
```

In summary, the `GetShuffledArrayExample` contract demonstrates how to use the `GeneralRandcastConsumerBase` to request a shuffled array of elements from a randomness `Adapter` and store the received shuffled arrays.


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