PSP22 Metadata

This example shows how you can reuse the implementation of PSP22 token with the PSP22Metadata extension.

First, you should implement basic version of PSP22.

Step 1: Add imports and enable unstable feature

Use openbrush::contract macro instead of ink::contract. Import everything from openbrush::contracts::psp22::extensions::metadata.

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

#[openbrush::implementation(PSP22, PSP22Metadata)]
#[openbrush::contract]
pub mod my_psp22 {
    ...

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 implementation.

#[ink(storage)]
#[derive(Default, Storage)]
pub struct Contract {
    #[storage_field]
    psp22: psp22::Data,
    #[storage_field]
    metadata: metadata::Data,
}

Step 3: Define constructor

Define constructor. Your PSP22Metadata contract is ready!

impl Contract {
    #[ink(constructor)]
    pub fn new(total_supply: Balance, name: Option<String>, symbol: Option<String>, decimal: u8) -> Self {
        let mut instance = Self::default();
        let caller = instance.env().caller();

        instance.metadata.name.set(&name);
        instance.metadata.symbol.set(&symbol);
        instance.metadata.decimals.set(&decimal);

        psp22::Internal::_mint_to(&mut instance, caller, total_supply).expect("Should mint total_supply");

        instance
    }
}

Final code

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

#[openbrush::implementation(PSP22, PSP22Metadata)]
#[openbrush::contract]
pub mod my_psp22 {
    use openbrush::traits::Storage;

    #[ink(storage)]
    #[derive(Default, Storage)]
    pub struct Contract {
        #[storage_field]
        psp22: psp22::Data,
        #[storage_field]
        metadata: metadata::Data,
    }

    impl Contract {
        #[ink(constructor)]
        pub fn new(total_supply: Balance, name: Option<String>, symbol: Option<String>, decimal: u8) -> Self {
            let mut instance = Self::default();
            let caller = instance.env().caller();

            instance.metadata.name.set(&name);
            instance.metadata.symbol.set(&symbol);
            instance.metadata.decimals.set(&decimal);

            psp22::Internal::_mint_to(&mut instance, caller, total_supply).expect("Should mint total_supply");

            instance
        }
    }
}

You can check an example of the usage of PSP22 Metadata.