nested-structs-in-solidity-are-annoying.sol

pragma solidity ^0.8.6;

contract SimpleStorage {
    struct A {
        uint256 id;
    }
    struct B {
        A[] ids;
        bool active;
    }

    B[] public bs;

    mapping(uint256 => B) public bstorage;

    constructor() public {
        /// @dev try #1:
        /// @notice TypeError: Invalid type for argument in function call. Invalid implicit conversion from struct SimpleStorage.A[2] memory to struct SimpleStorage.A[] memory requested
        // bs[0] = B({active: true, ids: [A({id: 1}))]});

        /// -
        /// @dev try #2:
        /// @notice TypeError: Member "push" is not available in struct SimpleStorage.A[] memory outside of storage.
        // A[] memory a;
        // a.push(A({id: 1}));
        // bs[0] = B({active: true, ids: a});

        /// -
        /// @dev try #3:
        /// @notice Copying of type struct SimpleStorage.A memory[] memory to storage not yet supported.
        // A[] memory a = new A[](1);
        // a[0] = A({id: 1});
        // bs[0] = B({active: true, ids: a});

        /// -
        /// @dev try #4:
        /// @notice UnimplementedFeatureError: Copying of type struct SimpleStorage.A memory[] memory to storage not yet supported.
        // B memory b = B(new A[](1), true);
        // bs.push(b);

        /// -
        /// @dev try #5
        /// @notice this actually works
        {
            B storage b = bs.push();
            b.active = true;
            for (uint256 i = 0; i < 2; i++) {
                b.ids.push(A({id: i}));
            }
        }

        /// what if we want to use a mapping?

        /// @dev try storage #1
        /// @notice TypeError: Invalid type for argument in function call. Invalid implicit conversion from struct SimpleStorage.A[1] memory to struct SimpleStorage.A[] memory requested.
        // bstorage[0] = B({active: true, ids: [A({id: 1})]});

        /// @dev try storage #2
        /// @notice UnimplementedFeatureError: Copying of type struct SimpleStorage.A memory[] memory to storage not yet supported.
        // A[] memory a = new A[](1);
        // a[0] = A({id: 1});
        // bstorage[0] = B({active: true, ids: a});

        /// @dev try storage #3
        /// @notice This works
        B storage b_a = bstorage[0];
        b_a.active = true;

        /// nope
        /// @notice UnimplementedFeatureError: Copying of type struct SimpleStorage.A memory[] memory to storage not yet supported.
        // A[] memory a = new A[](1);
        // a[0] = A({id: 1});
        // b_a.ids = a;

        b_a.ids[0] = A({id: 1});
        b_a.ids[1] = A({id: 2});

        /// @dev try storage #5
        /// @notice this works too
        {
            bstorage[0].active = true;
            bstorage[0].ids[0] = A({id: 1});
        }
    }
}

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