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This example shows how you can reuse the implementation of PSP34 token. Also, this example shows how you can customize the logic, for example, to track the number of tokens minted with next_id, increasing it with each new token minted, securing a unique id for each token.

Step 1: Include dependencies#

Include brush as dependency in the cargo file or you can use default Cargo.toml template. After you need to enable default implementation of PSP34 via brush features.

brush = { tag = "v1.6.1", git = "", default-features = false, features = ["psp34"] }

Step 2: Add imports and enable unstable feature#

Use brush::contract macro instead of ink::contract. Import everything from brush::contracts::psp34.

#![cfg_attr(not(feature = "std"), no_std)]#![feature(min_specialization)]
#[brush::contract]pub mod my_psp34 {    use brush::contracts::psp34::*;    use ink_storage::traits::SpreadAllocate;

Step 3: Define storage#

Declare storage struct and declare the field related to the PSP34Storage trait. Then you need to derive the PSP34Storage trait and mark the corresponding field with the #[PSP34StorageField] attribute. Deriving this trait allows you to reuse the default implementation of PSP34.

#[ink(storage)]#[derive(Default, SpreadAllocate, PSP34Storage)]pub struct MyPSP34 {    #[PSP34StorageField]    psp34: PSP34Data,}

Step 4: Inherit logic#

Inherit implementations of PSP34 and PSP34Metadata traits. You can customize (override) methods in this impl block.

impl PSP34 for MyPSP34 {}

Step 5: Define constructor#

Define constructor. Your basic version of PSP34 contract is ready!

impl MyPSP34 {    #[ink(constructor)]    pub fn new() -> Self {        ink_lang::codegen::initialize_contract(|_instance: &mut Self| {})    }}

Step 6: Customize your contract#

Customize it by adding logic for tracking the number of minted tokens. It will contain a custom mint_token function which will handle the id of the newly minted token. Also, we will add the next_id: u8 field to the structure, which will be increased with each newly minted token. This way we will make sure there will always be added a token with a unique id.

#[ink(storage)]#[derive(Default, SpreadAllocate, PSP34Storage)]pub struct MyPSP34 {    #[PSP34StorageField]    psp34: PSP34Data,    next_id: u8,}
impl PSP34 for MyPSP34 {}
impl MyPSP34 {    #[ink(constructor)]    pub fn new() -> Self {        ink_lang::codegen::initialize_contract(|_instance: &mut Self| {})    }
    #[ink(message)]    pub fn mint_token(&mut self) -> Result<(), PSP34Error> {        self._mint_to(Self::env().caller(), Id::U8(self.next_id))?;        self.next_id += 1;        Ok(())    }}

You can check an example of the usage of PSP34. Also you can use extensions for psp34 token:

PSP34Metadata: metadata for PSP34.

PSP34Mintable: creation of new tokens.

PSP34Burnable: destruction of contract's tokens.