PSP22 Pallet Metadata

This example shows how you can reuse the implementation of PSP22 token with the PSP22Metadata extension via pallet-assets chain extension.

First, you should implement basic version of PSP22 Pallet.

Step 1: Implement features

• Use openbrush::contract macro instead of ink::contract.
• Implement PSP22PalletMetadata via `#[openbrush::implementation].

#![cfg_attr(not(feature = "std"), no_std, no_main)]

#[openbrush::contract]
#[openbrush::implementation(PSP22Pallet, PSP22PalletMetadata)]
pub mod my_psp22_pallet {
    ...
}

Step 2: Define storage

Declare storage struct and declare the field related to the metadata module data structure. Then you need to derive the Storage trait and mark the corresponding field with the #[storage_field] attribute. Deriving this trait allows you to reuse the PSP22Metadata extension in your PSP22 Pallet implementation.

#[ink(storage)]
#[derive(Default, Storage)]
pub struct Contract {
    #[storage_field]
    pallet: psp22_pallet::Data,
}

Step 3: Define constructor

Define constructor. Your PSP22Metadata contract is ready!

impl Contract {
    /// During instantiation of the contract, you need to pass native tokens as a deposit
    /// for asset creation.
    #[ink(constructor)]
    #[ink(payable)]
    pub fn new(
        asset_id: u32,
        min_balance: Balance,
        total_supply: Balance,
        name: String,
        symbol: String,
        decimal: u8,
    ) -> Self {
        let mut instance = Self::default();

        psp22_pallet::Internal::_create(&mut instance, asset_id, Self::env().account_id(), min_balance)
            .expect("Should create an asset");
        instance.pallet.asset_id.set(&asset_id);
        instance.pallet.origin.set(&Origin::Caller);
        instance
            .pallet
            .pallet_assets
            .get_or_default()
            .set_metadata(asset_id, name.into(), symbol.into(), decimal)
            .expect("Should set metadata");
        psp22_pallet::Internal::_mint_to(&mut instance, Self::env().caller(), total_supply).expect("Should mint");

        instance
    }
}

Final code

#![cfg_attr(not(feature = "std"), no_std, no_main)]

#[openbrush::implementation(PSP22Pallet, PSP22PalletMetadata)]
#[openbrush::contract]
pub mod my_psp22_pallet_metadata {
    use openbrush::traits::Storage;

    #[ink(storage)]
    #[derive(Default, Storage)]
    pub struct Contract {
        #[storage_field]
        pallet: psp22_pallet::Data,
    }

    impl Contract {
        /// During instantiation of the contract, you need to pass native tokens as a deposit
        /// for asset creation.
        #[ink(constructor)]
        #[ink(payable)]
        pub fn new(
            asset_id: u32,
            min_balance: Balance,
            total_supply: Balance,
            name: String,
            symbol: String,
            decimal: u8,
        ) -> Self {
            let mut instance = Self::default();

            psp22_pallet::Internal::_create(&mut instance, asset_id, Self::env().account_id(), min_balance)
                .expect("Should create an asset");
            instance.pallet.asset_id.set(&asset_id);
            instance.pallet.origin.set(&Origin::Caller);
            instance
                .pallet
                .pallet_assets
                .get_or_default()
                .set_metadata(asset_id, name.into(), symbol.into(), decimal)
                .expect("Should set metadata");
            psp22_pallet::Internal::_mint_to(&mut instance, Self::env().caller(), total_supply).expect("Should mint");

            instance
        }
    }
}