Program Derived Address

In this section, we'll walk through how to build a basic CRUD (Create, Read, Update, Delete) program.

We'll create a simple program where users can create, update, and delete a message. Each message will be stored in an account with a deterministic address derived from the program itself (Program Derived Address or PDA).

The purpose of this section is to guide you through building and testing a Solana program using the Anchor framework while demonstrating how to use Program Derived Addresses (PDAs). For more details, refer to the Program Derived Addresses page.

For reference, here is the final code after completing both the PDA and CPI sections.

Starter Code

Begin by opening this Solana Playground link with the starter code. Then click the "Import" button, which will add the program to your list of projects on Solana Playground.

Import Import

In the lib.rs file, you'll find a program scaffolded with the create, update, and delete instructions we'll implement in the following steps.

lib.rs

use anchor_lang::prelude::*;

declare_id!("8KPzbM2Cwn4Yjak7QYAEH9wyoQh86NcBicaLuzPaejdw");

#[program]
pub mod pda {
    use super::*;

    pub fn create(_ctx: Context<Create>) -> Result<()> {
        Ok(())
    }

    pub fn update(_ctx: Context<Update>) -> Result<()> {
        Ok(())
    }

    pub fn delete(_ctx: Context<Delete>) -> Result<()> {
        Ok(())
    }
}

#[derive(Accounts)]
pub struct Create {}

#[derive(Accounts)]
pub struct Update {}

#[derive(Accounts)]
pub struct Delete {}

#[account]
pub struct MessageAccount {}

Before we begin, run build in the Playground terminal to check the starter program builds successfully.

Terminal

build

Define Message Account Type

First, let's define the structure for the message account that our program will create. This is the data that we'll store in the account created by the program.

In lib.rs, update the MessageAccount struct with the following:

lib.rs

#[account]
pub struct MessageAccount {
    pub user: Pubkey,
    pub message: String,
    pub bump: u8,
}

Build the program again by running build in the terminal.

Terminal

build

We've just defined what data to store on the message account. Next, we'll implement the program instructions.

Implement Create Instruction

Now, let's implement the create instruction to create and initialize the MessageAccount.

Start by defining the accounts required for the instruction by updating the Create struct with the following:

lib.rs

#[derive(Accounts)]
#[instruction(message: String)]
pub struct Create<'info> {
    #[account(mut)]
    pub user: Signer<'info>,

    #[account(
        init,
        seeds = [b"message", user.key().as_ref()],
        bump,
        payer = user,
        space = 8 + 32 + 4 + message.len() + 1
    )]
    pub message_account: Account<'info, MessageAccount>,
    pub system_program: Program<'info, System>,
}

Next, implement the business logic for the create instruction by updating the create function with the following:

lib.rs

pub fn create(ctx: Context<Create>, message: String) -> Result<()> {
    msg!("Create Message: {}", message);
    let account_data = &mut ctx.accounts.message_account;
    account_data.user = ctx.accounts.user.key();
    account_data.message = message;
    account_data.bump = ctx.bumps.message_account;
    Ok(())
}

Rebuild the program.

Terminal

build

Implement Update Instruction

Next, implement the update instruction to update the MessageAccount with a new message.

Just as before, the first step is to specify the accounts required by the update instruction.

Update the Update struct with the following:

lib.rs

#[derive(Accounts)]
#[instruction(message: String)]
pub struct Update<'info> {
    #[account(mut)]
    pub user: Signer<'info>,

    #[account(
        mut,
        seeds = [b"message", user.key().as_ref()],
        bump = message_account.bump,
        realloc = 8 + 32 + 4 + message.len() + 1,
        realloc::payer = user,
        realloc::zero = true,
    )]
    pub message_account: Account<'info, MessageAccount>,
    pub system_program: Program<'info, System>,
}

Next, implement the logic for the update instruction.

lib.rs

pub fn update(ctx: Context<Update>, message: String) -> Result<()> {
    msg!("Update Message: {}", message);
    let account_data = &mut ctx.accounts.message_account;
    account_data.message = message;
    Ok(())
}

Rebuild the program

Terminal

build

Implement Delete Instruction

Next, implement the delete instruction to close the MessageAccount.

Update the Delete struct with the following:

lib.rs

#[derive(Accounts)]
pub struct Delete<'info> {
    #[account(mut)]
    pub user: Signer<'info>,

    #[account(
        mut,
        seeds = [b"message", user.key().as_ref()],
        bump = message_account.bump,
        close= user,
    )]
    pub message_account: Account<'info, MessageAccount>,
}

Next, implement the logic for the delete instruction.

lib.rs

pub fn delete(_ctx: Context<Delete>) -> Result<()> {
    msg!("Delete Message");
    Ok(())
}

Rebuild the program.

Terminal

build

Deploy Program

The basic CRUD program is now complete. Deploy the program by running deploy in the Playground terminal.

Ensure your Playground wallet has devnet SOL. Get devnet SOL from the Solana Faucet.

Terminal

deploy

Set Up Test File

Included with the starter code is also a test file in anchor.test.ts.

anchor.test.ts

import { PublicKey } from "@solana/web3.js";

describe("pda", () => {
  it("Create Message Account", async () => {});

  it("Update Message Account", async () => {});

  it("Delete Message Account", async () => {});
});

Add the code below inside describe, but before the it sections.

anchor.test.ts

const program = pg.program;
const wallet = pg.wallet;

const [messagePda, messageBump] = PublicKey.findProgramAddressSync(
  [Buffer.from("message"), wallet.publicKey.toBuffer()],
  program.programId,
);

Run the test file by running test in the Playground terminal to check the file runs as expected. We will implement the tests in the following steps.

Terminal

test

Invoke Create Instruction

Update the first test with the following:

anchor.test.ts

it("Create Message Account", async () => {
  const message = "Hello, World!";
  const transactionSignature = await program.methods
    .create(message)
    .accounts({
      messageAccount: messagePda,
    })
    .rpc({ commitment: "confirmed" });

  const messageAccount = await program.account.messageAccount.fetch(
    messagePda,
    "confirmed",
  );

  console.log(JSON.stringify(messageAccount, null, 2));
  console.log(
    "Transaction Signature:",
    `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
  );
});

Invoke Update Instruction

Update the second test with the following:

anchor.test.ts

it("Update Message Account", async () => {
  const message = "Hello, Solana!";
  const transactionSignature = await program.methods
    .update(message)
    .accounts({
      messageAccount: messagePda,
    })
    .rpc({ commitment: "confirmed" });

  const messageAccount = await program.account.messageAccount.fetch(
    messagePda,
    "confirmed",
  );

  console.log(JSON.stringify(messageAccount, null, 2));
  console.log(
    "Transaction Signature:",
    `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
  );
});

Invoke Delete Instruction

Update the third test with the following:

anchor.test.ts

it("Delete Message Account", async () => {
  const transactionSignature = await program.methods
    .delete()
    .accounts({
      messageAccount: messagePda,
    })
    .rpc({ commitment: "confirmed" });

  const messageAccount = await program.account.messageAccount.fetchNullable(
    messagePda,
    "confirmed",
  );

  console.log("Expect Null:", JSON.stringify(messageAccount, null, 2));
  console.log(
    "Transaction Signature:",
    `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
  );
});

Run Test

Once the tests are set up, run the test file by running test in the Playground terminal.

Terminal

test

You can then inspect the SolanaFM links to view the transaction details.

Output

Diff

Explanation

Diff

Explanation

Diff

Explanation

Diff

Explanation

Diff

Explanation

Diff

Explanation

Diff

Explanation

Output

Diff

Explanation

Output

Diff

Explanation

Diff

Explanation

Diff

Explanation

Output

Mục lục