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Magic Actions Example

Explore reference implementation on GitHub

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1) Create action instruction

The instruction update_leaderboard runs on the base layer immediately after commit. 
// program instruction
pub fn update_leaderboard(ctx: Context<UpdateLeaderboard>) -> Result<()> {
    let leaderboard = &mut ctx.accounts.leaderboard;
    let counter_info = &mut ctx.accounts.counter.to_account_info();
    let mut data: &[u8] = &counter_info.try_borrow_data()?;
    let counter = Counter::try_deserialize(&mut data)?;

    if counter.count > leaderboard.high_score {
        leaderboard.high_score = counter.count;
    }

    msg!(
        "Leaderboard updated! High score: {}",
        leaderboard.high_score
    );
    Ok(())
}

// instruction context
#[action]
#[derive(Accounts)]
pub struct UpdateLeaderboard<'info> {
    #[account(mut, seeds = [LEADERBOARD_SEED], bump)]
    pub leaderboard: Account<'info, Leaderboard>,
    /// CHECK: PDA owner depends on: 1) Delegated: Delegation Program; 2) Undelegated: Your program ID
    pub counter: UncheckedAccount<'info>,
}

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2) Build the commit instruction with the action

The commit instruction commit_and_update_leaderboard runs on the ER and schedules the commit with action. 
// commit action instruction on ER
pub fn commit_and_update_leaderboard(ctx: Context<CommitAndUpdateLeaderboard>) -> Result<()> {
    let instruction_data =
        anchor_lang::InstructionData::data(&crate::instruction::UpdateLeaderboard {});

    let action_args = ActionArgs::new(instruction_data);

    let action_accounts = vec![
        ShortAccountMeta {
            pubkey: ctx.accounts.leaderboard.key(),
            is_writable: true,
        },
        ShortAccountMeta {
            pubkey: ctx.accounts.counter.key(),
            is_writable: false,
        },
    ];
    let action = CallHandler {
        destination_program: crate::ID,
        accounts: action_accounts,
        args: action_args,
        escrow_authority: ctx.accounts.payer.to_account_info(), // Signer authorized to pay transaction fees for action from escrow PDA
        compute_units: 200_000,
    };
    let magic_action = MagicInstructionBuilder {
        payer: ctx.accounts.payer.to_account_info(),
        magic_context: ctx.accounts.magic_context.to_account_info(),
        magic_program: ctx.accounts.magic_program.to_account_info(),
        magic_action: MagicAction::Commit(CommitType::WithHandler {
            commited_accounts: vec![ctx.accounts.counter.to_account_info()],
            call_handlers: vec![action],
        }),
    };
    magic_action.build_and_invoke()?;
    Ok(())
}

// commit action context on ER
#[commit]
#[derive(Accounts)]
pub struct CommitAndUpdateLeaderboard<'info> {
    #[account(mut)]
    pub payer: Signer<'info>,

    #[account(mut, seeds = [TEST_PDA_SEED], bump)]
    pub counter: Account<'info, Counter>,

    /// CHECK: Leaderboard PDA - not mut here, writable set in handler
    #[account(seeds = [LEADERBOARD_SEED], bump)]
    pub leaderboard: UncheckedAccount<'info>,

    /// CHECK: Your program ID
    pub program_id: AccountInfo<'info>,
}

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Execute multiple actions

You can commit multiple accounts and chain several actions. Actions execute sequentially. 
let magic_builder = MagicInstructionBuilder {
    payer: ctx.accounts.payer.to_account_info(),
    magic_context: ctx.accounts.magic_context.to_account_info(),
    magic_program: ctx.accounts.magic_program.to_account_info(),
    magic_action: MagicAction::Commit(CommitType::WithHandler {
        commited_accounts: vec![ctx.accounts.counter.to_account_info(), ...],
        call_handlers: vec![call_handler, ...],
    }),
};