5.5 原生资产(Native Assets)

The FuelVM has built-in support for working with multiple assets.

FuelVM内置了对多种资产工作的支持。

What does this mean in practice?

这在实践中意味着什么？

As in the EVM, sending ETH to an address or contract is an operation built into the FuelVM, meaning it doesn't rely on the existence of some token smart contract to update balances to track ownership.

与EVM一样，向地址或合约发送ETH是FuelVM内置的操作，这意味着它不依赖于一些代币智能合约的存续而进行余额更新进而追踪所有权。

However, unlike the EVM, the process for sending any native asset is the same. This means that while you would still need a smart contract to handle the minting and burning of fungible tokens, the sending and receiving of these tokens can be done independently of the token contract.

然而，与EVM不同，发送任何本地资产的过程都是一样的。这意味着，虽然你仍然需要一个智能合约来处理可替换代币的铸造和燃烧，但这些代币的发送和接收可以独立于代币合约完成。

流动资金池实例 (Liquidity Pool Example)

All contracts in Fuel can mint and burn their own native token. Contracts can also receive and transfer any native asset including their own. Internal balances of all native assets pushed through calls or minted by the contract are tracked by the FuelVM and can be queried at any point using the balance_of function from the std library. Therefore, there is no need for any manual accounting of the contract's balances using persistent storage.

Fuel的所有合约都可以铸造和燃烧自己的原生代币。合约也可以接收和转移任何本地资产，包括其自己的。所有通过调用推送或由合同铸造的本地资产，其内部余额由FuelVM跟踪，并可以在任何时候使用std库的 balance_of 函数进行查询。因此，不需要使用持久性存储对合约的余额进行任何人工核算。

The std library provides handy methods for accessing Fuel's native assset operations.

std库提供了方便的方法来访问Fuel的本地assset操作。

In this example, we show a basic liquidity pool contract minting its own native asset LP token.

在这个例子中，我们展示了一个基本的流动性池合约，铸造自己的本地资产LP代币。

contract;

use std::{
    call_frames::{
        contract_id,
        msg_asset_id,
    },
    context::msg_amount,
    token::{
        mint_to_address,
        transfer_to_address,
    },
};

abi LiquidityPool {
    fn deposit(recipient: Address);
    fn withdraw(recipient: Address);
}

const BASE_TOKEN = ContractId::from(0x9ae5b658754e096e4d681c548daf46354495a437cc61492599e33fc64dcdc30c);

impl LiquidityPool for Contract {
    fn deposit(recipient: Address) {
        assert(msg_asset_id() == BASE_TOKEN);
        assert(msg_amount() > 0);

        // Mint two times the amount.
        let amount_to_mint = msg_amount() * 2;

        // Mint some LP token based upon the amount of the base token.
        mint_to_address(amount_to_mint, recipient);
    }

    fn withdraw(recipient: Address) {
        assert(msg_asset_id() == contract_id());
        assert(msg_amount() > 0);

        // Amount to withdraw.
        let amount_to_transfer = msg_amount() / 2;

        // Transfer base token to recipient.
        transfer_to_address(amount_to_transfer, BASE_TOKEN, recipient);
    }
}

原生代币实例 (Native Token Example)

In this example, we show a native token contract with more minting, burning and transferring capabilities.

在这个例子中，我们展示了一个具有更多铸币，燃烧和转移能力的本地代币合约。

contract;

use std::{context::*, token::*};

abi NativeAssetToken {
    fn mint_coins(mint_amount: u64);
    fn burn_coins(burn_amount: u64);
    fn force_transfer_coins(coins: u64, asset_id: ContractId, target: ContractId);
    fn transfer_coins_to_output(coins: u64, asset_id: ContractId, recipient: Address);
    fn deposit();
    fn get_balance(target: ContractId, asset_id: ContractId) -> u64;
    fn mint_and_send_to_contract(amount: u64, destination: ContractId);
    fn mint_and_send_to_address(amount: u64, recipient: Address);
}

impl NativeAssetToken for Contract {
    /// Mint an amount of this contracts native asset to the contracts balance.
    fn mint_coins(mint_amount: u64) {
        mint(mint_amount);
    }

    /// Burn an amount of this contracts native asset.
    fn burn_coins(burn_amount: u64) {
        burn(burn_amount);
    }

    /// Transfer coins to a target contract.
    fn force_transfer_coins(coins: u64, asset_id: ContractId, target: ContractId) {
        force_transfer_to_contract(coins, asset_id, target);
    }

    /// Transfer coins to a transaction output to be spent later.
    fn transfer_coins_to_output(coins: u64, asset_id: ContractId, recipient: Address) {
        transfer_to_address(coins, asset_id, recipient);
    }

    /// Get the internal balance of a specific coin at a specific contract.
    fn get_balance(target: ContractId, asset_id: ContractId) -> u64 {
        balance_of(target, asset_id)
    }

    /// Deposit tokens back into the contract.
    fn deposit() {
        assert(msg_amount() > 0);
    }

    /// Mint and send this contracts native token to a destination contract.
    fn mint_and_send_to_contract(amount: u64, destination: ContractId) {
        mint_to_contract(amount, destination);
    }

    /// Mind and send this contracts native token to a destination address.
    fn mint_and_send_to_address(amount: u64, recipient: Address) {
        mint_to_address(amount, recipient);
    }
}