ERC 721 (NFT) module

⚠️

This module is unaudited and may change in the future.

The erc721-puppet (opens in a new tab) module lets you create ERC-721 (opens in a new tab) NFTs as part of a MUD World. The advantage of doing this, rather than creating a separate NFT contract (opens in a new tab) and merely controlling it from MUD, is that all the information is in MUD tables and is immediately available in the client.

Deployment

The easiest way to deploy this module is to edit mud.config.ts. This is a modified version of the vanilla template.

Note that before you use this file you need to run pnpm add viem (see explanation below).

mud.config.ts

import { defineWorld } from "@latticexyz/world";
import { encodeAbiParameters, stringToHex } from "viem";
 
const erc721ModuleArgs = encodeAbiParameters(
  [
    { type: "bytes14" },
    {
      type: "tuple",
      components: [{ type: "string" }, { type: "string" }, { type: "string" }],
    },
  ],
  [stringToHex("MyNFT", { size: 14 }), ["No Valuable Token", "NVT", "http://www.example.com/base/uri/goes/here"]],
);
 
export default defineWorld({
  namespace: "app",
  tables: {
    Counter: {
      schema: {
        value: "uint32",
      },
      key: [],
    },
  },
  modules: [
    {
      artifactPath: "@latticexyz/world-modules/out/PuppetModule.sol/PuppetModule.json",
      root: false,
      args: [],
    },
    {
      artifactPath: "@latticexyz/world-modules/out/ERC721Module.sol/ERC721Module.json",
      root: false,
      args: [
        {
          type: "bytes",
          value: erc721ModuleArgs,
        },
      ],
    },
  ],
});

Explanation

import { encodeAbiParameters, stringToHex } from "viem";

In simple cases it is enough to use the config parser to specify the module arguments. However, the NFT module requires a struct as one of the arguments (opens in a new tab). We use encodeAbiParameters (opens in a new tab) to encode the struct data. The stringToHex (opens in a new tab) function is used to specify the namespace the token uses.

This is the reason we need to issue pnpm install viem in packages/contracts to be able to use the library here.

const erc721ModuleArgs = encodeAbiParameters(

You can see the arguments for the ERC-721 module here (opens in a new tab). There are two arguments:

A 14-byte identifier for the namespace.
An ERC721MetadataData for the ERC-721 parameters, defined here (opens in a new tab).

However, the arguments for a module are ABI encoded (opens in a new tab) to a single value of type bytes. So we use encodeAbiParameters from the viem library to create this argument. The first parameter of this function is a list of argument types.

  [
    { type: "bytes14" },

The first parameter is simple, a 14 byte value for the namespace.

    {
      type: "tuple",
      components: [{ type: "string" }, { type: "string" }, { type: "string" }],
    },
  ],

The second value is more complicated, it's a struct, or as it is called in ABI, a tuple. It consists of three strings (the token name, symbol, and base URI (opens in a new tab)).

  [
    stringToHex("MyNFT", { size: 14 }),

The second encodeAbiParameters parameter is a list of the values, of the types declared in the first list.

The first parameter for the module is bytes14, the namespace of the ERC-721 token. We use stringToHex (opens in a new tab) to convert it from the text form that is easy for us to use, to the hexadecimal number that Viem expects for bytes14 parameter.

    ["No Valuable Token", "NVT", "http://www.example.com/base/uri/goes/here"],
  ],
);

The second parameter for the module is a structure of three strings, so here we provide the three strings. Then we close all the definitions.

  modules: [
    {
      artifactPath: "@latticexyz/world-modules/out/PuppetModule.sol/PuppetModule.json",
      root: false,
      args: [],
    },

A module declaration requires three parameters:

artifactPath, a link to the compiled JSON file for the module.
root, whether to install the module with root namespace permissions or not.
args the module arguments.

Here we install the puppet module (opens in a new tab). We need this module because a System is supposed to be stateless, and easily upgradeable to a contract in a different address. However, both the ERC-20 standard (opens in a new tab) and the ERC-721 standard (opens in a new tab) require the token contract to emit events. The solution is to put the System in one contract and have another contract, the puppet, which receives requests and emits events according to the ERC.

    {
      artifactPath: "@latticexyz/world-modules/out/ERC721Module.sol/ERC721Module.json",
      root: false,
      args: [
        {
          type: "bytes",

The data type for this parameter is bytes, because it is treated as opaque bytes by the World and only gets parsed by the module after it is transferred.

          value: erc721ModuleArgs,
        },
      ],
    },

The module arguments, stored in erc721ModuleArgs.

Usage

You can use the token the same way you use any other ERC721 contract. For example, run this script.

ManageERC721.s.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.24;
 
import { Script } from "forge-std/Script.sol";
import { console } from "forge-std/console.sol";
import { StoreSwitch } from "@latticexyz/store/src/StoreSwitch.sol";
import { ResourceId } from "@latticexyz/store/src/ResourceId.sol";
import { RESOURCE_TABLE } from "@latticexyz/store/src/storeResourceTypes.sol";
import { WorldResourceIdLib } from "@latticexyz/world/src/WorldResourceId.sol";
import { ERC721Registry } from "@latticexyz/world-modules/src/codegen/index.sol";
import { IERC721Mintable } from "@latticexyz/world-modules/src/modules/erc721-puppet/IERC721Mintable.sol";
 
import { IWorld } from "../src/codegen/world/IWorld.sol";
 
contract ManageERC721 is Script {
  function run() external {
    address worldAddress = address(0x8D8b6b8414E1e3DcfD4168561b9be6bD3bF6eC4B);
 
    // Specify a store so that you can use tables directly in PostDeploy
    StoreSwitch.setStoreAddress(worldAddress);
 
    // Load the private key from the `PRIVATE_KEY` environment variable (in .env)
    uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");
    address myAddress = vm.addr(deployerPrivateKey);
 
    // Start broadcasting transactions from the deployer account
    vm.startBroadcast(deployerPrivateKey);
 
    // Get the ERC-721 token address
    ResourceId namespaceResource = WorldResourceIdLib.encodeNamespace(bytes14("MyNFT"));
    ResourceId erc721RegistryResource = WorldResourceIdLib.encode(RESOURCE_TABLE, "erc721-puppet", "ERC721Registry");
    address tokenAddress = ERC721Registry.getTokenAddress(erc721RegistryResource, namespaceResource);
    console.log("Token address", tokenAddress);
 
    // Settings to test with
    uint256 badGoatToken = uint256(0xBAD060A7);
    uint256 beefToken = uint256(0xBEEF);
    address goodGuy = address(0x600D);
    address badGuy = address(0x0BAD);
 
    // Use the token
    IERC721Mintable erc721 = IERC721Mintable(tokenAddress);
 
    // Mint two tokens
    erc721.mint(goodGuy, badGoatToken);
    erc721.mint(myAddress, beefToken);
    console.log("Owner of bad goat:", erc721.ownerOf(badGoatToken));
    console.log("Owner of beef:", erc721.ownerOf(beefToken));
 
    // Transfer a token
    erc721.transferFrom(myAddress, badGuy, beefToken);
    console.log("Owner of bad goat:", erc721.ownerOf(badGoatToken));
    console.log("Owner of beef:", erc721.ownerOf(beefToken));
 
    // Burn the tokens
    erc721.burn(badGoatToken);
    erc721.burn(beefToken);
 
    console.log("Done");
 
    vm.stopBroadcast();
  }
}

Explanation

    // Get the ERC-721 token address
    ResourceId namespaceResource = WorldResourceIdLib.encodeNamespace(bytes14("MyNFT"));
    ResourceId erc721RegistryResource =
      WorldResourceIdLib.encode(RESOURCE_TABLE, "erc721-puppet", "ERC721Registry");
    address tokenAddress = ERC721Registry.getTokenAddress(erc721RegistryResource, namespaceResource);
    console.log("Token address", tokenAddress);

This is the process to get the address of our token contract (the puppet). First, we get the resourceId values for the erc721-puppet__ERC721Registry table and the namespace we are interested in (each namespace can only have one ERC721 token). Then we use that table to get the token address.

    // Use the token
    IERC721Mintable erc721 = IERC721Mintable(tokenAddress);

Create an IERC721Mintable (opens in a new tab) for the token.

    // Mint two tokens
    erc721.mint(goodGuy, badGoatToken);
    erc721.mint(myAddress, beefToken);
    console.log("Owner of bad goat:", erc721.ownerOf(badGoatToken));
    console.log("Owner of beef:", erc721.ownerOf(beefToken));

Mint a couple of tokens, and show who owns them. Note that only the owner of the name space is authorized to mint tokens.

    // Transfer a token
    erc721.transferFrom(myAddress, badGuy, beefToken);
    console.log("Owner of bad goat:", erc721.ownerOf(badGoatToken));
    console.log("Owner of beef:", erc721.ownerOf(beefToken));

Transfer a token. We can only transfer tokens we own, or that we have approval to transfer from the current owner.

    // Burn the tokens
    erc721.burn(badGoatToken);
    erc721.burn(beefToken);

Destroy the tokens.

ERC-20 tokens Delegation (interface)