Attribute Macro pink::driver

#[driver]

This procedural macro marks an ink! trait as a ‘driver contract’ for the Pink system.

What is the driver system?

The driver system is a straightforward concept. In the Pink system, there is a registry mapping driver names to driver contract addresses. The System contract provides two methods to manage this registry: System::set_driver(driver_name, contract_address) and System::get_driver(driver_name).

How does this macro work?

When this attribute is used, it modifies the given trait to be utilized as a driver contract within the Pink system. This is achieved by adding a new type, TraitNameRef, which implements the marked trait and provides a static method instance() to retrieve an instance of the driver.

Example

Below, the SidevmOperation trait is annotated with #[pink::driver]. This marks it as a driver contract, enabling it to manage SideVM deployments.

#[pink::driver]
#[ink::trait_definition]
pub trait SidevmOperation {
    #[ink(message)]
    fn deploy(&self, code_hash: Hash) -> Result<(), DriverError>;

    #[ink(message)]
    fn can_deploy(&self, contract_id: AccountId) -> bool;
}

Once a trait has been defined as a driver using this macro, it can be set as a driver by invoking the System::set_driver(driver_name, contract_address) method.

Usage

The actual driver can then be retrieved and its methods, defined by the trait, can be used. For instance, to start a SideVM, one would get the driver instance and call its deploy method:

pub fn start_sidevm(code_hash: Hash) -> Result<(), system::DriverError> {
    let driver =
        SidevmOperationRef::instance().ok_or(system::Error::DriverNotFound)?;
    driver.deploy(code_hash)
}

Here, SidevmOperationRef::instance() retrieves an instance of the driver contract for “SidevmOperation”, and then the deploy method of the driver is invoked to deploy a SideVM instance. Internally, SidevmOperationRef::instance() retrieves the driver contract by invoking System::get_driver("SidevmOperation").

Note: The name of the driver contract instance (e.g., “SidevmOperation”) is generated by the macro.