Struct anchor_lang::accounts::account_loader::AccountLoader

pub struct AccountLoader<'info, T: ZeroCopy + Owner> { /* private fields */ }

Type facilitating on demand zero copy deserialization.

Note that using accounts in this way is distinctly different from using, for example, the Account. Namely, one must call

• load_init after initializing an account (this will ignore the missing account discriminator that gets added only after the user’s instruction code)
• load when the account is not mutable
• load_mut when the account is mutable

For more details on zero-copy-deserialization, see the account attribute.

⚠️ When using this type it's important to be mindful of any calls to the load functions so as not to induce a RefCell panic, especially when sharing accounts across CPI boundaries. When in doubt, one should make sure all refs resulting from a call to a load function are dropped before CPI. This can be done explicitly by calling drop(my_var) or implicitly by wrapping the code using the Ref in braces {..} or moving it into its own function.

Example

use anchor_lang::prelude::*;

declare_id!("Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS");

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

    pub fn create_bar(ctx: Context<CreateBar>, data: u64) -> Result<()> {
        let bar = &mut ctx.accounts.bar.load_init()?;
        bar.authority = ctx.accounts.authority.key();
        bar.data = data;
        Ok(())
    }

    pub fn update_bar(ctx: Context<UpdateBar>, data: u64) -> Result<()> {
        (*ctx.accounts.bar.load_mut()?).data = data;
        Ok(())
    }
}

#[account(zero_copy)]
#[derive(Default)]
pub struct Bar {
    authority: Pubkey,
    data: u64
}

#[derive(Accounts)]
pub struct CreateBar<'info> {
    #[account(
        init,
        payer = authority
    )]
    bar: AccountLoader<'info, Bar>,
    #[account(mut)]
    authority: Signer<'info>,
    system_program: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct UpdateBar<'info> {
    #[account(
        mut,
        has_one = authority,
    )]
    pub bar: AccountLoader<'info, Bar>,
    pub authority: Signer<'info>,
}

Implementations

impl<'info, T: ZeroCopy + Owner> AccountLoader<'info, T>

pub fn try_from(
    acc_info: &AccountInfo<'info>
) -> Result<AccountLoader<'info, T>>

Constructs a new Loader from a previously initialized account.

pub fn try_from_unchecked(
    _program_id: &Pubkey,
    acc_info: &AccountInfo<'info>
) -> Result<AccountLoader<'info, T>>

Constructs a new Loader from an uninitialized account.

pub fn load(&self) -> Result<Ref<'_, T>>

Returns a Ref to the account data structure for reading.

pub fn load_mut(&self) -> Result<RefMut<'_, T>>

Returns a RefMut to the account data structure for reading or writing.

pub fn load_init(&self) -> Result<RefMut<'_, T>>

Returns a RefMut to the account data structure for reading or writing. Should only be called once, when the account is being initialized.

Trait Implementations

impl<'info, T: ZeroCopy + Owner> Accounts<'info> for AccountLoader<'info, T>

fn try_accounts(
    _program_id: &Pubkey,
    accounts: &mut &[AccountInfo<'info>],
    _ix_data: &[u8],
    _bumps: &mut BTreeMap<String, u8>,
    _reallocs: &mut BTreeSet<Pubkey>
) -> Result<Self>

Returns the validated accounts struct. What constitutes “valid” is program dependent. However, users of these types should never have to worry about account substitution attacks. For example, if a program expects a Mint account from the SPL token program in a particular field, then it should be impossible for this method to return Ok if any other account type is given–from the SPL token program or elsewhere.

impl<'info, T: ZeroCopy + Owner> AccountsClose<'info> for AccountLoader<'info, T>

This function is for INTERNAL USE ONLY. Do NOT use this function in a program. Manual closing of AccountLoader<'info, T> types is NOT supported.

Details: Using close with AccountLoader<'info, T> is not safe because it requires the mut constraint but for that type the constraint overwrites the “closed account” discriminator at the end of the instruction.

fn close(&self, sol_destination: AccountInfo<'info>) -> Result<()>

impl<'info, T: ZeroCopy + Owner> AccountsExit<'info> for AccountLoader<'info, T>

fn exit(&self, _program_id: &Pubkey) -> Result<()>

program_id is the currently executing program.

impl<'info, T: ZeroCopy + Owner> AsRef<AccountInfo<'info>> for AccountLoader<'info, T>

fn as_ref(&self) -> &AccountInfo<'info>

Converts this type into a shared reference of the (usually inferred) input type.

impl<'info, T: Clone + ZeroCopy + Owner> Clone for AccountLoader<'info, T>

fn clone(&self) -> AccountLoader<'info, T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'info, T: ZeroCopy + Owner + Debug> Debug for AccountLoader<'info, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'info, T: ZeroCopy + Owner> Key for AccountLoader<'info, T>

fn key(&self) -> Pubkey

impl<'info, T: ZeroCopy + Owner> ToAccountInfos<'info> for AccountLoader<'info, T>

fn to_account_infos(&self) -> Vec<AccountInfo<'info>>

impl<'info, T: ZeroCopy + Owner> ToAccountMetas for AccountLoader<'info, T>

fn to_account_metas(&self, is_signer: Option<bool>) -> Vec<AccountMeta>

is_signer is given as an optional override for the signer meta field. This covers the edge case when a program-derived-address needs to relay a transaction from a client to another program but sign the transaction before the relay. The client cannot mark the field as a signer, and so we have to override the is_signer meta field given by the client.