## Gear 合约开发案例解析 - OnChain NFT
<p align="center">
<a href="https://gitpod.io/#https://github.com/gear-foundation/dapps-on-chain-nft">
<img src="https://gitpod.io/button/open-in-gitpod.svg" width="240" alt="GEAR">
</a>
</p>
代码仓库: https://github.com/gear-foundation/dapps-on-chain-nft
本 PPT 链接: https://hackmd.io/@btwiuse/on-chain-nft
---
How Do Off-Chain NFTs Work?
[wiki](https://wiki.gear-tech.io/docs/examples/gnft-721/) | [example](https://gear-non-fungible-token.vercel.app/nft/0) | [contract](https://idea.gear-tech.io/state/full/0xd48e2451dbb32de3e7d73623dc4b172a3f13eb1faf0a0cd89186513a0469bf00?node=wss%3A%2F%2Ftestnet.vara.rs)
```
{
"name": "Genesis",
"description": "genesis nft",
"media": "Qmf3WTdCiDPD5mfP3N6jKU3WfHGLB6LtkBGo5AKEMRJNRR",
"reference": "QmQ3sFAbF9Ry39NGS2GUnzXCvYybRbYVm9qL4TBxac9PMj"
}
```
- reference (NFT Attributes): [QmQ3...9PMj](https://ipfs-gw.gear-tech.io/ipfs/QmQ3sFAbF9Ry39NGS2GUnzXCvYybRbYVm9qL4TBxac9PMj)
- media (NFT Image): [Qmf3...JNRR](https://ipfs-gw.gear-tech.io/ipfs/Qmf3WTdCiDPD5mfP3N6jKU3WfHGLB6LtkBGo5AKEMRJNRR)
---
What’s The Problem With Off-Chain NFTs?
- Off-chain NFTs are usually stored on a server, cloud storage, or IPFS somewhere.
- In any event, if the storage service is disrupted or completely goes down for whatever reason, the link will lead to nowhere and the asset will not be accessible.
---
Introducing On-Chain NFTs
- Firstly, when initializing a collection, one should provide all the possible images of all the layers for a collection.
- Secondly, when minting alongside with a small metadata, one should provide a combination of layers used for a specific NFT.
This approach seems quite costly when initializing, but is relatively cheap when it comes to minting.
---
例如，创建一个 背景+人物 形式的 NFT 集合，需要下列图层
```
[
[
"#黑色[0]",
"#白色[1]",
"#蓝色[2]"
],
[
"#李小龙[0]",
"#青眼白龙[1]"
]
]
```
总共可能有 3x2 种不同组合: {00, 01, 10, 11, 20, 21}
---
参考 Wiki https://wiki.gear-tech.io/docs/examples/onchain-nft
<p align="center">
<a href="https://gitpod.io/#https://github.com/gear-foundation/dapps-on-chain-nft">
<img src="https://gitpod.io/button/open-in-gitpod.svg" width="240" alt="GEAR">
</a>
</p>
代码仓库:
- 传统 NFT 合约 https://github.com/gear-foundation/dapps-non-fungible-token
- 纯链上 NFT 合约 https://github.com/gear-foundation/dapps-on-chain-nft
---
## build
```
$ make build
```
## download
```
./on_chain_nft.meta.txt
./target/wasm32-unknown-unknown/release/on_chain_nft.opt.wasm
./target/wasm32-unknown-unknown/release/onchain_nft_state.meta.wasm
```
## deploy
https://idea.gear-tech.io/?node=wss://testnet.vara.rs
---
## 课后作业
本期作业: 在 [Vara Stable Testnet](https://idea.gear-tech.io/?node=wss://testnet.vara.rs) 上部署 https://github.com/gear-foundation/dapps-on-chain-nft 合约，并与合约交互，创建多个图层，并 Mint 出所有可能的组合
---
# Questions
<img src="https://hackmd.io/_uploads/SyK8P72d2.jpg" width="240" alt="GEAR">
<img src="https://hackmd.io/_uploads/By_kgE3_2.png" width="240" alt="VARA">
课后答疑频道: https://t.me/Gear_CN
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