CODEWITHSUNDEEP
soliditynftrsk
Owans
Owans

Reputation: 1037

How can I tell if a smart contract on RSK is an NFT?

Given an address of a smart contract deployed to RSK, how can I tell if it is an NFT or not? Is there a "standard" way to do this?

Upvotes: 4

Views: 494

Answers (1)

bguiz
bguiz

Reputation: 28617

Yes there is a definitive way to do this, if the smart contracts implement well-known token standards for NFTs, which in turn implement the well-known EIP165 Standard Interface Definition.

(1) The easiest way to do this is to simply look up the address on the RSK block explorer.

If the smart contract address is 0x814eb350813c993df32044f862b800f91e0aaaf0, then go to https://explorer.rsk.co/address/0x814eb350813c993df32044f862b800f91e0aaaf0

On this page, you will see a row for "Contract Interfaces", and in the case of this smart contract, displays ERC165 ERC721 ERC721Enumerable ERC721Metadata. Since this contains ERC721, we know that it implements that token standard for non-fungible tokens.

(2) The more programmatic/ DIY way to do this is to use the function defined in the EIP165 standard, whose interface is copied below:

interface ERC165 {
    /// @notice Query if a contract implements an interface
    /// @param interfaceID The interface identifier, as specified in ERC-165
    /// @dev Interface identification is specified in ERC-165. This function
    ///  uses less than 30,000 gas.
    /// @return `true` if the contract implements `interfaceID` and
    ///  `interfaceID` is not 0xffffffff, `false` otherwise
    function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

Without going too much into the math of how this is calculated, (read the EIP-165 standard for the full description/ explanation) if invoking supportsInterface returns true, then you know that that this smart contracts (claims to) implement that particular interface.

  • If you wish to test if a particular smart contract implements the "Non-Fungible Token Standard":
    • call supportsInterface(0x80ac58cd)
  • If you wish to test if a particular smart contract implements the "Multi Token Standard", which is presently the 2nd most popular NFT standard:
    • call supportsInterface(0xd9b67a26)

(Note that while both of the above values are stated in their respective standards, you may also wish to calculate them yourself, and the EIP-165 standard includes section on how to do this.)

Upvotes: 6

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