NFT Template Contract that works out of the box!

This Replit template allows users to immediately deploy and play with an ERC721 NFT contract that is ready to mint, trade, and withdraw on approved marketplaces. This replit features an easy to use interface website for interacting with the contract once it is deployed.

Features include:

Hot reloading
Solidity error checking
Deploying multiple contracts
UI for testing out contracts
A mixin contract architecture that allows users to plug-and-play the features they'd like included for their NFT.

Getting started

Just press the Run ▶️ button!

You should only need to do this once (and might take like 15s). This will install all relevant packages, start up the contract deployment UI, and compile your contract.sol file.
contract.sol is just an import file that brings in the NFT.sol contract, which is the 'atomic unit' contract that can be deployed and actually played with.
Pressing cmd-s or ctrl-s (windows) will reload the UI.

We have preinstalled packages from @openzeppelin/contracts. To install other solidity packages that are distributed on npm, make sure you install them using the Package Installer 📦 in the sidebar

Basic contract

Implements the barebones methods needed to have a functioning NFT.sol, so that users can start out with a simpler implementation and build up to more complex contracts if they wish. To use this implementation, remove the mixins from the contract declaration and replace any overrides(FooMixin, BarMixin) in NFT.sol with just overrides.

Mixins

These are single-purpose implementations of the same base contract ERC721Tradable.sol. Each comes with a corresponding role that is automatically granted to the deploying address, but can be added to other accounts via the grantRole() contract call or removed via the revokeRole() call.

There are several different mixins users can choose to add or remove from their implementation:

MinterMixin: Adds minting utils and some gas-saving and a Solidity counter to avoid messing up tokenId generation. Also includes logic for having a maximum amount of tokens to mint in the collection. Finally, add a special minter role that gives only role-havers the ability to mint tokens, conceptually an on-chain allowlist for minting.
OperatorMixin: Adds some gas-saving features by allowing third-parties such as OpenSea to transact on an owner's behalf by granting them an Operator role.
WithdrawMixin: Your 10K Snail PFP collection finished minting in 30 seconds, now what? You want to cash in on that sweet fake internet money? Welllll its going to be stuck in the smart contract forever if you don't include this mixin or something similar to it.

Future work

I cannot for the life of me figure out why I can't put the contracts into a dedicated folder, but the whole things crashes when I do that

Harden the mixin architecture further to make it easier to extend and add more interesting implementations that can be plugged in easily.

Some thoughts so far include splitting out minting into more subfeatures like:

1 mint per account
Mass minting to save gas
Randomizing tokenIds

Some other mixins could be:

Burn mixin
Pausable mixin
An on-chain renderer mixin for 8-bit art

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