销毁 NEP-141 代币

问题描述

我想实现OpenZepplin's ERC20 library提供的_burn(address account,uint256 amount)函数。当某些条件为真时，智能合约将调用此函数。

Rust fungible token example 有一个 on_tokens_burned() 函数，但它看起来像一个记录器。

    fn on_tokens_burned(&mut self,account_id: AccountId,amount: Balance) {
        log!("Account @{} burned {}",account_id,amount);
    }

如何销毁特定用户的代币？

解决方法

以下是burn的一些实现：


    pub fn burn(&mut self,amount: U128String){
        let balance = self.internal_unwrap_balance_of(env::predecessor_account_id());
        assert!(balance>=amount);
        self.internal_update_account(&env::predecessor_account_id(),balance - amount);
        assert!(self.total_supply>=amount);
        self.total_supply -= amount;
    }

    /// Inner method to save the given account for a given account ID.
    /// If the account balance is 0,the account is deleted instead to release storage.
    pub fn internal_update_account(&mut self,account_id: &AccountId,balance: u128) {
        if balance == 0 {
            self.accounts.remove(account_id);
        } else {
            self.accounts.insert(account_id,&balance); //insert_or_update
        }
    }

    pub fn internal_unwrap_balance_of(&self,account_id: &AccountId) -> Balance {
        match self.accounts.get(&account_id) {
            Some(balance) => balance,None => 0,}
    }

我们在这里使用了类似的东西：https://github.com/alpha-fi/cheddar/blob/master/cheddar/src/internal.rs

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