Constructor

Constructors are a special type of function that runs only once when deploying a contract, and can be used to initialize the state of the contract. Your contract must not have more than one constructor, and that constructor function must be annotated with the #[constructor] attribute. Also, a good practice consists in naming that function constructor.

Here's a simple example that demonstrates how to initialize the state of a contract on deployment by defining logic inside a constructor.

#[starknet::contract]
pub mod ExampleConstructor {
    use starknet::ContractAddress;
    use starknet::storage::{Map, StorageMapWriteAccess};
 
    #[storage]
    struct Storage {
        pub names: Map::<ContractAddress, felt252>,
    }
 
    // The constructor is decorated with a `#[constructor]` attribute.
    // It is not inside an `impl` block.
    #[constructor]
    fn constructor(ref self: ContractState, name: felt252, address: ContractAddress) {
        self.names.write(address, name);
    }
}