Cw721 Base (Soulbound)

This is a basic implementation of a cw721 NFT contract. It implements the CW721 spec (soulbound) and is designed to be deployed as is, or imported into other contracts to easily build cw721-compatible NFTs with custom logic.

"Soulbound" is implemented by removing transfer_nft and send_nft from the cw721-base package.

Implements:

• CW721 Base
• Metadata extension
• Enumerable extension

Implementation

The ExecuteMsg and QueryMsg implementations follow the CW721 spec and are described there; however, the transfer_nft and send_nft entry points are removed to enforce non-transferability of the NFT assets, thereby making them "soulbound". Beyond that, we make a few additions:

• InstantiateMsg takes name and symbol (for metadata), as well as a Minter address. This is a special address that has full power to mint new NFTs (but not modify existing ones)
• ExecuteMsg::Mint{token_id, owner, token_uri, extension} - creates a new token with given owner and (optional) metadata. It can only be called by the Minter set in instantiate.
• ExecuteMsg::Update{token_id, extension} - updates a token's metadata provided permissions criteria are satisfied.
• QueryMsg::Minter{} - returns the minter address for this contract.

It requires all tokens to have defined metadata in the standard format (with no extensions). For generic NFTs this may often be enough.

The Minter can either be an external actor (e.g. web server, using PubKey) or another contract. If you just want to customize the minting behavior but not other functionality, you could extend this contract (importing code and wiring it together) or just create a custom contract as the owner and use that contract to Mint.

If provided, it is expected that the token_uri points to a JSON file following the ERC721 Metadata JSON Schema.

Running this contract

You will need Rust 1.44.1+ with wasm32-unknown-unknown target installed.

You can run unit tests on this via:

cargo test

Once you are happy with the content, you can compile it to wasm via:

RUSTFLAGS='-C link-arg=-s' cargo wasm
cp ../../target/wasm32-unknown-unknown/release/cw721_soulbound.wasm .
ls -l cw721_soulbound.wasm
sha256sum cw721_soulbound.wasm

Or for a production-ready (optimized) build, run a build command in the repository root: https://github.com/CosmWasm/cw-plus#compiling.

Importing this contract

You can also import much of the logic of this contract to build another CW721-compliant contract, such as tradable names, crypto kitties, or tokenized real estate.

Basically, you just need to write your handle function and import cw721_base_soulbound::contract::mint, etc and dispatch to them. This allows you to use custom ExecuteMsg and QueryMsg with your additional calls, but then use the underlying implementation for the standard cw721 messages (except transfer_nft and send_nft which cannot be invoked). The same with QueryMsg. You will most likely want to write a custom, domain-specific instantiate.