PSP22 FlashMint

This example shows how you can reuse the implementation of PSP22 token with PSP22FlashMint extension, which allows the user to perform a flash loan on the token by minting the borrowed amount and then burning it along with fees for the loan.

1. Implement the FlashMint extension

First, you should implement basic version of PSP22.

After you can just add implementation of PSP22Flashmint via #[openbrush::implementation(PSP22Flashmint)] attribute.

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

#[openbrush::implementation(PSP22, Flashmint)]
#[openbrush::contract]
pub mod my_psp22_flashmint {
    use openbrush::traits::Storage;

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

    /// Override `get_fee` function to add 1% fee to the borrowed `amount`
    #[overrider(flashmint::Internal)]
    fn _get_fee(&self, amount: Balance) -> Balance {
        amount / 100
    }

    impl Contract {
        #[ink(constructor)]
        pub fn new(total_supply: Balance) -> Self {
            let mut instance = Self::default();
            psp22::Internal::_mint_to(&mut instance, Self::env().caller(), total_supply).expect("Should mint");

            instance
        }
    }
}

And that's it! Your PSP22 is now extended by the PSP22FlashMint extension and ready to use its functions! You can check the full example of the implementation of this extension here.