How to mapping a struct EnumerableSet.AddressSet / UintSet?

External question — Ethereum Stack Exchange Author: hellcodediver Original post: https://ethereum.stackexchange.com/questions/120650 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. Hello guys I want to make mapping but got some issues. pragma solidity ^0.8.4; import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol"; contract fNftErc20 { using EnumerableSet for EnumerableSet.AddressSet; using EnumerableSet for EnumerableSet.UintSet; struct fCollection{ EnumerableSet.AddressSet nftAddress; EnumerableSet.UintSet nftIds; bool mintable; } mapping(address => fCollection) private fractionalizationCollections; function ad(address fnft, address[] calldata nft, uint256[] calldata id) public { EnumerableSet.AddressSet lockedNft; EnumerableSet.UintSet lockedId; for(uint256 i = 0; i<nft.length; i++){ lockedId.add(id[i]); lockedNft.add(nft[i]); } fractionalizationCollections[fnft] = fCollection(lockedNft, lockedId, true); } } I want make something like this but dont know how make it true. If someone got idea please share with, thanks so much)))

External answer — Ethereum Stack Exchange Author: MShakeG Original post: https://ethereum.stackexchange.com/a/148082 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. The errors you are encountering are because you cannot assign a struct containing (nested) mappings directly, and you cannot construct a struct containing (nested) mappings. Additionally lockedNft and lockedId cannot be declared locally i.e. in memory since AddressSet and UintSet contain mappings, and so while they can be moved into contract state i.e. storage since this would be gas heavy you can instead add the nft address and id onto a given fCollection as shown below. In short, to fix these issues, you can update your contract by removing the direct assignments and constructors for the fCollection struct, and instead use a two-step process to update the mappings inside the struct. Here's the updated contract: pragma solidity ^0.8.4; import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol"; contract fNftErc20 { using EnumerableSet for EnumerableSet.AddressSet; using EnumerableSet for EnumerableSet.UintSet; struct fCollection { EnumerableSet.AddressSet nftAddress; EnumerableSet.UintSet nftIds; bool mintable; } mapping(address => fCollection) private fractionalizationCollections; function ad(address fnft, address[] calldata nft, uint256[] calldata id) public { // Check if the fCollection does not exist for the given fnft address require( !fractionalizationCollections[fnft].mintable, "fCollection already exists for the given fnft address" ); // Initialize the fCollection for the given fnft address fractionalizationCollections[fnft].mintable = true; for (uint256 i = 0; i < nft.length; i++) { fractionalizationCollections[fnft].nftIds.add(id[i]); fractionalizationCollections[fnft].nftAddress.add(nft[i]); } } }