hello-nft

Hello, NFT!

From Wikipedia,

A non-fungible token (NFT) is a unique and non-interchangeable unit of data stored on a digital ledger (blockchain). NFTs can be associated with easily-reproducible items such as photos, videos, audio, and other types of digital files as unique items

In this example, we will show you how to build a ticket vending machine in Scrypto.

Blueprint and Component

The blueprint we're building is called HelloNft. Each HelloNft manages the following resources and data.

struct HelloNft {
    /// A vault that holds all available tickets.
    available_tickets: Vault,
    /// The price for each ticket.
    ticket_price: Decimal,
    /// A vault for collecting payments.
    collected_xrd: Vault,
}

The available_tickets contains non-fungible Ticket resource. Both fungible and non-fungible resources are stored in a Vault.

Creating NFT Units

In our example, the supply of NFT units are fixed, and we allocate the resource upfront.

First, we prepare the data for each NFT unit (every ticket is associated with a specific row and column number).

let mut tickets: Vec<(StringNonFungibleLocalId, Ticket)> = Vec::new();
for row in 1..5 {
    for column in 1..5 {
        tickets.push((
            StringNonFungibleLocalId::new(format!("ticket_{}{}", row, column)).unwrap(),
            Ticket { row, column },
        ));
    }
}

Then, the whole vector of NFT data is passed to ResourceBuilder as the initial supply.

let ticket_bucket = ResourceBuilder::new_string_non_fungible(OwnerRole::None)
    .metadata(metadata!( 
        init {
            "name" => "Ticket".to_owned(), locked;
        }
    ))
    .mint_initial_supply(tickets);

After that, we get a bucket of NFT units stored in ticket_bucket.

Allowing Callers to Buy Tickets

A HelloNft component exposes three public methods:

• buy_ticket: allowing caller to buy one ticket;
• buy_ticket_by_id: allowing caller to buy one specific ticket;
• available_ticket_ids: returns the IDs of all available tickets.

The workflow of buy_ticket and buy_ticket_by_id is very similar.

self.collected_xrd.put(payment.take(self.ticket_price));
let ticket = self.available_tickets.take(1);
// OR let ticket = self.available_tickets.take_non_fungible(id);
(ticket, payment)

Both involves

1. Taking a payment according to pre-defined price and putting it into the collected_xrd vault;
2. Taking a ticket from the available_tickets vault:
   • take(1) returns one NFT unit;
   • take_non_fungible(id) returns the specified NFT unit.
3. Returning the ticket and payment change.

How to Play?

1. Create a new account, and save the account address

resim new-account

2. Publish the package, and save the package address

resim publish .

3. Call the instantiate_hello_nft function to instantiate a component, and save the component address

resim call-function <PACKAGE_ADDRESS> HelloNft instantiate_hello_nft 5

4. Call the available_ticket_ids

resim call-method <COMPONENT_ADDRESS> available_ticket_ids

5. Call the buy_ticket method

resim call-method <COMPONENT_ADDRESS> buy_ticket "100,resource_sim1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqz8qety"

6. Call the buy_ticket_by_id method

resim call-method <COMPONENT_ADDRESS> buy_ticket_by_id ticket_44 "100,resource_sim1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqz8qety"

7. Check out our balance

resim show <ACCOUNT_ADDRESS>