Create a Non-Fungible Token
On Sui, everything is an object. Moreover, everything is a non-fungible token (NFT) as its objects are unique, non-fungible, and owned.
Creating NFTs on Sui differs from other blockchains that are not object based. Those blockchains require a dedicated standard to handle the properties that define NFTs because they are based on a mapping between smart contracts and the token's ID. For instance, the ERC-721 standard on Ethereum was necessary to pair a globally unique ID with the relevant smart contract address to create a unique token instance on the network.
On Sui, every object already has a unique ID, so whether you're dealing with a million fungible tokens, like coins, or thousands of NFTs with individual characteristics, like SuiFrens, your smart contracts on Sui always interact with individual objects.
Imagine you create an Excitable Chimp NFT collection on Sui and another blockchain that isn't object based. To get an attribute like the Chimp's name on the other blockchain, you would need to interact with the smart contract that created the NFT to get that information (typically from off-chain storage) using the NFT ID. On Sui, the name attribute can be a field on the object that defines the NFT itself. This construct provides a much more straightforward process for accessing metadata for the NFT as the smart contract that wants the information can just return the name from the object itself.
Example
The following example creates a basic NFT on Sui. The TestnetNFT struct defines the NFT with an id, name, description, and url fields.
public struct TestnetNFT has key, store {
id: UID,
name: string::String,
description: string::String,
url: Url,
}
In this example, anyone can mint the NFT by calling the mint_to_sender function. As the name suggests, the function creates a new TestnetNFT and transfers it to the address that makes the call.
#[allow(lint(self_transfer))]
public fun mint_to_sender(
name: vector<u8>,
description: vector<u8>,
url: vector<u8>,
ctx: &mut TxContext
) {
let sender = ctx.sender();
let nft = TestnetNFT {
id: object::new(ctx),
name: string::utf8(name),
description: string::utf8(description),
url: url::new_unsafe_from_bytes(url)
};
event::emit(NFTMinted {
object_id: object::id(&nft),
creator: sender,
name: nft.name,
});
transfer::public_transfer(nft, sender);
}
The module includes functions to return NFT metadata, too. Referencing the hypothetical used previously, you can call the name function to get that value. As you can see, the function simply returns the name field value of the NFT itself.
public fun name(nft: &TestnetNFT): &string::String {
&nft.name
}
Toggle complete source code
module examples::testnet_nft {
use sui::url::{Self, Url};
use std::string;
use sui::event;
/// An example NFT that can be minted by anybody
public struct TestnetNFT has key, store {
id: UID,
/// Name for the token
name: string::String,
/// Description of the token
description: string::String,
/// URL for the token
url: Url,
// TODO: allow custom attributes
}
// ===== Events =====
public struct NFTMinted has copy, drop {
// The Object ID of the NFT
object_id: ID,
// The creator of the NFT
creator: address,
// The name of the NFT
name: string::String,
}
// ===== Public view functions =====
/// Get the NFT's `name`
public fun name(nft: &TestnetNFT): &string::String {
&nft.name
}
/// Get the NFT's `description`
public fun description(nft: &TestnetNFT): &string::String {
&nft.description
}
/// Get the NFT's `url`
public fun url(nft: &TestnetNFT): &Url {
&nft.url
}
// ===== Entrypoints =====
#[allow(lint(self_transfer))]
/// Create a new devnet_nft
public fun mint_to_sender(
name: vector<u8>,
description: vector<u8>,
url: vector<u8>,
ctx: &mut TxContext
) {
let sender = ctx.sender();
let nft = TestnetNFT {
id: object::new(ctx),
name: string::utf8(name),
description: string::utf8(description),
url: url::new_unsafe_from_bytes(url)
};
event::emit(NFTMinted {
object_id: object::id(&nft),
creator: sender,
name: nft.name,
});
transfer::public_transfer(nft, sender);
}
/// Transfer `nft` to `recipient`
public fun transfer(
nft: TestnetNFT, recipient: address, _: &mut TxContext
) {
transfer::public_transfer(nft, recipient)
}
/// Update the `description` of `nft` to `new_description`
public fun update_description(
nft: &mut TestnetNFT,
new_description: vector<u8>,
_: &mut TxContext
) {
nft.description = string::utf8(new_description)
}
/// Permanently delete `nft`
public fun burn(nft: TestnetNFT, _: &mut TxContext) {
let TestnetNFT { id, name: _, description: _, url: _ } = nft;
id.delete()
}
}
Related links
- NFT Rental: Example that rents NFTs using Kiosk Apps.
- Kiosk: Asset storage on the Sui network.
- Kiosk Apps: Extend the functionality of the Kiosk standard.