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91 lines
3.3 KiB
Markdown
91 lines
3.3 KiB
Markdown
2 years ago
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# Tips
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## Transfers
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For users, it is more gas optimal to transfer bulk minted tokens in ascending token ID order.
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For example, if you have bulk minted token IDs (33, 34, ..., 99),
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you should transfer in the order (33, 34, ..., 99).
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This is due to how the lazy-initialization mechanism works internally:
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it scans uninitialized slots in descending order until it finds an initialized slot.
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## Popularity
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The more popular your NFT collection, the larger the expected savings in transaction fees.
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See [Design: Lower Fees](design.md#lower-fees).
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## Aux
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Consider using [`ERC721A._getAux`](erc721a.md#_getAux) and
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[`ERC721A._setAux`](erc721a.md#_setAux) to get / set per-address variables
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(e.g. number of whitelist mints per address).
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This can help remove an extra cold `SLOAD` and `SSTORE` operation.
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## Minting
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For typical artwork collections, consider using `_mint` over `_safeMint` if you don't expect users to mint to contracts.
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## Batch Size
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During transfers, ERC721A scans through ownership storage slots until it finds an initialized slot.
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To prevent expensive first-time transfer fees for tokens minted in large batches, either:
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- Restrict the max batch size for public mints to a reasonable number.
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- Break up excessively large batches into mini batches internally when minting.
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- Use [`_initializeOwnershipAt`](erc721a.md#_initializeOwnershipAt) every couple tokens to reduce number of reads during a transfer.
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## Efficient Tokenomics
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ERC721A keeps track of additional variables in the internal mappings.
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- [`startTimestamp`](erc721a.md#_ownershipOf) (starting time of holding) per token.
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- [`numberMinted`](erc721a.md#_numberMinted) per address.
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- [`numberBurned`](erc721a.md#_numberBurned) per address.
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These variables hitchhike on the `SLOAD`s and `SSTORE`s at near zero additional gas cost (< 1%).
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You can use them to design tokenomics with very minimal gas overhead.
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> The [`startTimestamp`](erc721a.md#_ownershipOf), is available via the
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> [`TokenOwnership`](erc721a.md#TokenOwnership) struct.
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>
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> You can get it from the
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> [`_ownershipOf`](erc721a.md#_ownershipOf) function or the non-reverting
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> [`ERC721AQueryable.explicitOwnershipOf`](erc721a-queryable.md#explicitOwnershipOf) function.
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## ERC721A vs ERC1155
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| | ERC721A | ERC1155 |
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| ---------------- | -------------- | ---------------------- |
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| O(1) ownerOf | Yes | No ownerOf |
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| O(1) balanceOf | For all tokens | Within fungible tokens |
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| O(1)\* bulk mint | For all tokens | Within fungible tokens |
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| # mint `SSTORE`s | 3 | 1 <sup>†</sup> |
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\* Approximately O(1) for ERC721A. See [Design](design.md).
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<sup>†</sup> For unique collections, ERC1155 needs a counter which needs 1 more `SSTORE`.
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ERC1155 requires centralized indexing services to emulate ERC721-like functionality off-chain.
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## Other Implementations
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ERC721A is not a one-size-fits-all solution.
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It is heavily optimized for generative artwork NFT collections.
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If your collection does not expect a busy mint phase (e.g. a pure utility NFT),
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or does not require bulk minting,
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these excellent implementations can be better for lowering overall transaction fees:
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- [OpenZeppelin](https://github.com/OpenZeppelin/openzeppelin-contracts)
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- [Solmate](https://github.com/Rari-Capital/solmate)
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Use the right tool for the job.
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