aztec-nr - noir_aztec::state_vars::single_private_immutable

Struct SinglePrivateImmutable

pub struct SinglePrivateImmutable<Note, Context>
{ /* private fields */ }

A state variable that holds a single private value that is set once and remains unchanged forever (unlike crate::state_vars::private_immutable::PrivateImmutable, which holds one private value per account - hence the name 'single').

Because this private value has no semantic owner, it is up to the application to determine which accounts will learn of its existence via crate::note::note_message::NoteMessage::deliver_to.

Usage

Unlike crate::state_vars::private_immutable::PrivateImmutable which is "owned" (requiring wrapping in an crate::state_vars::owned::Owned state variable), SinglePrivateImmutable is used directly in storage:

#[storage]
struct Storage<Context> {
    your_variable: SinglePrivateImmutable<YourNote, Context>,
}

Example

A contract's configuration parameters can be represented as a SinglePrivateImmutable. Once set during contract deployment or initial setup, these parameters remain constant for the lifetime of the contract. For example, an account contract's signing public key is typically stored using SinglePrivateImmutable. Note that the configuration would be visible only to the parties to which the NoteMessage returned from the initialize(...) function is delivered.

Requirements

The contract that holds this state variable must have keys associated with it. This is because the initialization nullifier includes the contract's nullifying secret key (nsk) in its preimage and because the contract is set as the owner of the underlying note. This is expected to not ever be a problem because the contracts that use SinglePrivateImmutable generally have keys associated with them (account contracts or escrow contracts).

Implementations

`impl<Note> SinglePrivateImmutable<Note, UtilityContext>`

pub unconstrained fn is_initialized(self) -> bool
where
    Note: NoteType,
    Note: NoteHash,
    Note: Eq

Returns whether this SinglePrivateImmutable has been initialized.

pub unconstrained fn view_note(self) -> Note
where
    Note: Packable,
    Note: NoteType,
    Note: NoteHash,
    Note: Eq

Returns the permanent note in this SinglePrivateImmutable state variable instance.

`impl<Note> SinglePrivateImmutable<Note, &mut PrivateContext>`

pub fn initialize(self, note: Note) -> NoteMessage<Note>
where
    Note: NoteType,
    Note: NoteHash,
    Note: Packable

Initializes a SinglePrivateImmutable state variable instance with a permanent note and returns a NoteMessage that allows you to decide what method of note message delivery to use.

This function inserts the single, permanent note for this state variable. It can only be called once per SinglePrivateImmutable. Subsequent calls will fail because the initialization nullifier will already exist.

pub fn get_note(self) -> Note
where
    Note: NoteType,
    Note: NoteHash,
    Note: Packable

Reads the permanent note of a SinglePrivateImmutable state variable instance.

If this SinglePrivateImmutable state variable has not yet been initialized, no note will exist: the call will fail and the transaction will not be provable.

Since the note is immutable, there's no risk of reading stale data or race conditions - the note never changes after initialization.

`impl<Context, Note> SinglePrivateImmutable<Note, Context>`

Trait implementations

`impl<Context, Note> StateVariable<1, Context> for SinglePrivateImmutable<Note, Context>`

pub fn new(context: Context, storage_slot: Field) -> Self pub fn get_storage_slot(self) -> Field