Smart Contract Cheat Sheet — Go, JS, Java & Solidity

// Fabric Chaincode — Go (asset CRUD)
func (c *AssetContract) CreateAsset(ctx contractapi.TransactionContextInterface,
    id, name, owner string, value int) error {

    exists, err := c.AssetExists(ctx, id)
    if err != nil {
        return fmt.Errorf("failed to check existence: %w", err)
    }
    if exists {
        return fmt.Errorf("asset %s already exists", id)
    }

    asset := Asset{ID: id, Name: name, Owner: owner, Value: value}
    assetJSON, err := json.Marshal(asset)
    if err != nil {
        return fmt.Errorf("failed to marshal: %w", err)
    }

    return ctx.GetStub().PutState(id, assetJSON)
}

// Besu Smart Contract — Solidity (asset CRUD)
contract AssetRegistry {
    struct Asset {
        string name;
        address owner;
        uint256 value;
        bool exists;
    }

    mapping(string => Asset) private assets;
    event AssetCreated(string indexed id, address owner);

    modifier onlyOwner(string memory id) {
        require(assets[id].owner == msg.sender, "Not owner");
        _;
    }

    function createAsset(string memory id, string memory name,
        uint256 value) external {
        require(!assets[id].exists, "Already exists");
        assets[id] = Asset(name, msg.sender, value, true);
        emit AssetCreated(id, msg.sender);
    }
}