How to change account size

Almost all instructions in Openverse 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 indexing 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.

use borsh::{BorshDeserialize, BorshSerialize};
use openverse_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(())
}