# erc721 — NFT (ERC-721 port)

> ⚠️ **Experimental — generated with no human supervision** by the daily MCP pipeline (Solidity→Gno port). Not audited. See [r/moul/x/daily](https://github.com/moul/gno-contracts/blob/main/r/moul/x/daily/README.md).

---


An idiomatic gno.land port of the Solidity **ERC-721** non-fungible token
standard. Each token is a unique, sequentially-minted integer id owned by
exactly one address. Ownership, per-owner balances and single-token approvals
live in ordered `avl.Tree`s, so `Render` can list every token deterministically.
`msg.sender` maps to `unsafe.PreviousRealm().Address()`, `require` to `panic`,
and Solidity events to `chain.Emit` (`Mint`, `Transfer`, `Approval`).

## Transactions
- `Mint(cur realm, to address) int64` — mint the next token id to `to`; returns the id.
- `Transfer(cur realm, to address, id int64)` — move a token you own (or are approved for) to `to`; clears the approval.
- `Approve(cur realm, spender address, id int64)` — owner grants `spender` the right to transfer token `id`.

## Read-only
- `OwnerOf(id int64) address` — owner of a token (panics if it does not exist).
- `BalanceOf(owner address) uint64` — number of tokens held by `owner`.
- `TotalSupply() int64` — total tokens in circulation.
- `Render(path string)` — Markdown: total supply + a token → owner → approved table.

## Example
```
Mint(cur, g1alice...)          // -> tokenID 1
Mint(cur, g1alice...)          // -> tokenID 2
Approve(cur, g1bob..., 1)      // alice approves bob for token 1
Transfer(cur, g1carol..., 1)   // owner alice sends token 1 to carol
OwnerOf(1)                     // -> g1carol...
BalanceOf(g1alice...)          // -> 1
TotalSupply()                  // -> 2
```

<!-- BEGIN GNOCONTRACTS FOOTER (generated by `make readmes`; do not edit below) -->

---

Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

**Dependency graph:**

![gno.land/r/moul/x/daily/erc721/v0 dependency graph](https://raw.githubusercontent.com/moul/gno-contracts/main/_assets/gno.land/r/moul/x/daily/erc721/v0/deps.png)

> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

<!-- END GNOCONTRACTS FOOTER -->