How to read accounts in a program
Almost all instructions in Solana require at least 2 - 3 accounts, and they
would be mentioned over the instruction handlers on what order it's expecting those
set of accounts. It's fairly simple if we take advantage of the iter() method in
Rust, instead of manually indicing the accounts. The next_account_info method basically
slices the first index of the iterable and returning the account present inside the
accounts array. Let's see a simple instruction which expects a bunch of accounts
and requiring to parse each of them.
read-accounts.rs
use borsh::{BorshDeserialize, BorshSerialize};
use solana_program::{
account_info::{next_account_info, AccountInfo},
entrypoint,
entrypoint::ProgramResult,
pubkey::Pubkey,
};
entrypoint!(process_instruction);
#[derive(BorshSerialize, BorshDeserialize, Debug)]
pub struct HelloState {
is_initialized: bool,
}
// Accounts required
/// 1. [signer] Payer
/// 2. [writable] Hello state account
/// 3. [] Rent account
/// 4. [] System Program
pub fn process_instruction(
_program_id: &Pubkey,
accounts: &[AccountInfo],
_instruction_data: &[u8],
) -> ProgramResult {
// Fetching all the accounts as a iterator (facilitating for loops and iterations)
let accounts_iter = &mut accounts.iter();
// Payer account
let payer_account = next_account_info(accounts_iter)?;
// Hello state account
let hello_state_account = next_account_info(accounts_iter)?;
// Rent account
let rent_account = next_account_info(accounts_iter)?;
// System Program
let system_program = next_account_info(accounts_iter)?;
Ok(())
}