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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.