Hi all, we now have improved documentation for the InfinitySwap IC CDK. Copied here for convenience. We have now introduced a new killer feature which brings inheritance to our Rust canister development kit. You can now override methods from other canisters!
canister-sdk
An SDK for writing and testing canisters for the Internet Computer in Rust. This repo includes a few crates that help to
simplify the tricky aspects of IC canisters development:
This project builds on top of ic-cdk and ic-kit crates. It is not intended to replace them, but adds some types and
macros to simplify things that are not dealt with by those crates.
Crates
ic-canister
This crate introduces a framework to write easily testable canisters, including testing inter-canister communications,
as well as a way to compose a canister APIs using rust traits. There are a few examples bellow, but for the details
check out the crate documentation.
Inter-canister calls and testing
For example, you can have a canister with simple API:
#[derive(Clone, Canister)]
struct MyCanister {
#[id]
principal: Principal,
#[state]
state: Rc<RefCell<MyCanisterState>>,
}
impl MyCanister {
#[query]
fn get_counter(&self) -> u64 {
self.state.borrow().counter
}
#[update]
fn add(&self, value: u64) {
self.state.borrow_mut().counter += value;
}
}
Now instead of using ic_cdk::api::call to query these APIs from another canister doing manual
serialization/deserialization:
impl MyOtherCanister {
#[update]
async fn increment_get(&self, id: Principal) -> u64 {
let my_canister = MyCanister::from_principal(id);
canister_call!(my_canister.add(1), ()).await.unwrap();
let updated_value = canister_call!(my_canister.get_counter(), u64).await.unwrap();
updated_value
}
}
Now, if you want to test the increment_get method of you canister, all you need to do is to write a unit test:
#[tokio::test]
async fn test_increment_get() {
let my_canister = MyCanister::init_instance();
let my_other_canister = MyOtherCanister::init_instance();
assert_eq!(my_other_canister.increment_get(my_canister.principal()), 1);
assert_eq!(my_other_canister.increment_get(my_canister.principal()), 2);
}
Even though the canisters use statics internally to store the state, the tests can initialize multiple instances of
canisters with init_instance method, and each one of them will have a separate state.
Canister state and upgrades
When using Canister derive macro, the fields that are marked with #[state] attribute are all preserved over canister upgrades. This is done using Versioned trait. This means that at this moment you can have only one #[state] in a canister. If the state type is changed, the new state must have the previous state type as its Versioned::Previous
type. The Canister derive macro take care of generating the pre_upgrade and post_upgrade functions and updating
the state to the new type when needed.
If a canister needs to have a state that is not preserved during the upgrade process (like caches or some other temporary data), #[state(stable_store = false)] can be used in addition to the #[state] field. Any number of non-stable state fields can be added to a canister.
Canister traits and composition
It is also possible to write a canister trait to store some part of API to be reused in different canisters. You can find an example of such a trait in the ic_factory::api module. This also allows to compose a canister from different traits just by implementing the needed traits for your canister struct:
impl Factory for MyCanister {
fn state(&self) -> Rc<RefCell<FactoryState>> {
self.factory_state.clone()
}
}
impl OtherCanisterTrait for MyCanister {
// impl
}
NOTE: this part of the SDK is still work in progress, so some parts of it are subject to change
Dependencies between canisters
If you use ic-cdk to create your canister’s APIs, you cannot simply use a canister as a rust dependency for another canister, because all the APIs of the dependency will also be included into the dependent canister. If you create a canister using canister-sdk, just add a no_api feature to your canister. When this feature is enabled on a dependency, the API of the dependency will not be exported white the rest of logic and types can be used in you crate.
ic-factory
Base of a canister factory canister. The Factory canister trait can be used to simply write a canister factory for canisters of you type. It also provides a convenient way to upgrade all the canister that the factory is set to manage.
ic-helpers
This crate contains some types, helper functions and re-exports for ic repo. These are just used for convenience and the overall structure of the crate is not finalized (and some stuff is outdated and will be removed in the future).
ic-storage
Introduces traits IcStorage and Versioned for in-memory and stable storage management respectively.
In-memory storage
In the past, the ic-cdk crate provided methods in the ic_cdk::storage module to store and get structs from the canister’s memory, but they were removed in version 0.5.0 (for a good reason). The recommended way to store the data in the canister memory is to use thread_local storage with RefCell controlling access to the struct.
The ic_storage::IcStorage derive macro does exactly, but saving you some boilerplate. Using it is quite
straightforward:
use ic_storage::IcStorage;
#[derive(IcStorage, Default)]
struct MyCanisterState {
value: u32,
}
let local_state = MyCanisterState::get();
assert_eq!(local_state.borrow().value, 0);
local_state.borrow_mut().value = 42;
assert_eq!(local_state.borrow().value, 42);
It also allows having generic state structures. For detailed information, check out the crate level documentation.
Versioned state
The ic_storage::stable module introduces Versioned trait that allows transparent upgrades for you state on canister upgrades (event over several versions of state at once). When using this trait, the state structure can be serialized into the stable storage using ic_storage::stable::write method. Then after the upgrade, simply use
ic_storage::stable::read::<NewStateType>(). This will read the serialized previous version of the state, check its version and run the upgrade methods until the current version of the type (the NewStateType struct) is reached.
Check out the module level documentation for more details.