利息承載擴展

Name: 使用Web3.js的Token2022
Availability: InStock

InterestBearing 擴展是一個 Mint 賬戶擴展，允許用戶為其代幣應用利率，並在任何時刻檢索包括利息在內的更新總額。

初始化鑄幣賬戶

要在 InterestBearing 擴展上初始化 Mint 賬戶，我們需要使用 interestBearingMint() 函數。

以下是如何使用利息承載擴展創建鑄幣的方法：

import { Keypair, SystemProgram, Transaction, sendAndConfirmTransaction } from "@solana/web3.js";
import {
  createInitializeMintInstruction,
  createInitializeInterestBearingMintInstruction,
  getMintLen,
  ExtensionType,
  TOKEN_2022_PROGRAM_ID,
} from "@solana/spl-token";

const mint = Keypair.generate();

// Calculate the size needed for a Mint account with Interest Bearing extension
const mintLen = getMintLen([ExtensionType.InterestBearingConfig]);

// Calculate minimum lamports required for rent exemption
const lamports = await connection.getMinimumBalanceForRentExemption(mintLen);

// Create the account with the correct size and owner
const createAccountInstruction = SystemProgram.createAccount({
  fromPubkey: keypair.publicKey,
  newAccountPubkey: mint.publicKey,
  space: mintLen,
  lamports,
  programId: TOKEN_2022_PROGRAM_ID,
});

// Initialize the Interest Bearing extension
const initializeMintInterestBearing = createInitializeInterestBearingMintInstruction(
  mint.publicKey,
  keypair.publicKey,
  500,
  TOKEN_2022_PROGRAM_ID,
);

// Initialize the mint itself
const initializeMintInstruction = createInitializeMintInstruction(
  mint.publicKey,
  6,
  keypair.publicKey,
  null,
  TOKEN_2022_PROGRAM_ID,
);

// Combine all instructions in the correct order
const transaction = new Transaction().add(
  createAccountInstruction,
  initializeMintNonTransferable,
  initializeMintInstruction,
);

const signature = await sendAndConfirmTransaction(connection, transaction, [keypair, mint]);

console.log(
  `Mint created! Check out your TX here: https://explorer.solana.com/tx/${signature}?cluster=devnet`,
);

Expand

[40 more lines]

計算利息

InterestBearing 擴展不會生成新代幣；顯示的金額僅通過 amount_to_ui_amount 函數包括累積的利息，這使得更改僅僅是視覺上的。

因此，在 unpacking Token 賬戶以計算利息後，我們可以輕鬆獲取執行計算所需的所有信息以獲得利息金額。

幸運的是，我們甚至不需要這樣做，因為我們可以像這樣使用 amountToUiAmount 函數：

const tokenInfo = await getAccount(connection, tokenAccount, undefined, TOKEN_2022_PROGRAM_ID);

console.log("Token Amount: ", tokenInfo.amount);

const uiAmount = await amountToUiAmount(
  connection,
  keypair,
  mint.publicKey,
  tokenInfo.amount,
  TOKEN_2022_PROGRAM_ID,
);

console.log("UI Amount: ", uiAmount);

更新利息承載擴展

通過 InterestBearing 擴展，可以更改代幣賬戶產生的利息，這得益於其數據結構的設計：

rust

pub struct InterestBearing {
    pub rate_authority: Pubkey,
    pub initialization_timestamp: i64,
    pub pre_update_average_rate: u16,
    pub last_update_timestamp: i64,
    pub current_rate: u16,
}

為此，我們可以像這樣使用 updateRateInterestBearingMint 函數：

const updateRateInstruction = await createUpdateRateInterestBearingMintInstruction(
  mint.publicKey,
  newRateAuthority.publicKey,
  1000, // updated rate
  undefined,
  TOKEN_2022_PROGRAM_ID,
);

如果我們希望更改設置利息的權限，可以使用 setAuthority 函數並傳入正確的 AuthorityType，像這樣：

const setAuthorityInstruction = await createSetAuthorityInstruction(
  mint.publicKey,
  keypair.publicKey,
  AuthorityType.InterestRate,
  newRateAuthority.publicKey,
  [],
  TOKEN_2022_PROGRAM_ID,
);