Defining Initializer Functions

This page explains how to write an initializer function.

Initializers are regular functions that set an "initialized" flag (a nullifier) for the contract. A contract can only be initialized once, and contract functions can only be called after the contract has been initialized, much like a constructor. However, if a contract defines no initializers, it can be called at any time. Additionally, you can define as many initializer functions in a contract as you want, both private and public.

Annotate with #[aztec(private)] and #[aztec(initializer)]

Define your initializer like so:

#[aztec(private)]
#[aztec(initializer)]
fn constructor(){
    // function logic here
}

Initializer with logic

Initializers are commonly used to set an admin, such as this example:

constructor

#[aztec(public)]
#[aztec(initializer)]
fn constructor(admin: AztecAddress, name: str<31>, symbol: str<31>, decimals: u8) {
    assert(!admin.is_zero(), "invalid admin");
    storage.admin.write(admin);
    storage.minters.at(admin).write(true);
    storage.name.initialize(FieldCompressedString::from_string(name));
    storage.symbol.initialize(FieldCompressedString::from_string(symbol));
    storage.decimals.initialize(decimals);
}

^{_{Source code: noir-projects/noir-contracts/contracts/token_contract/src/main.nr#L56-L69}}

Here, the initializer is calling a public function. It can also call a private function. Learn more about calling functions from functions here.

To see an initializer in action, check out the Counter Contract Tutorial.