Kitties Map

Now let's learn to interact with our Kitties storage map, and update the map when we mint new kitties.

Basic APIs

This tutorial will only go over just the basic APIs needed to build our Pallet.

Check out the StorageMap documentation if you want to see the full APIs.

Reading Storage

To read the current value of a key in a StorageMap, you can simply call the get(key) API:

#![allow(unused)]
fn main() {
let my_key: [u8; 32] = [0u8; 32];
let maybe_value: Option<()> = Kitties::<T>::get(my_key);
}

Just as the StorageValue, you can see this query returns an Option, indicating whether there is actually a value under the key.

Just as before, the most ergonomic way to read a kitty, or throw an error when there is no kitty is to write the following:

#![allow(unused)]
fn main() {
let kitty: () = Kitties::<T>::get(my_key).ok_or(Error::<T>::NoKitty)?;
}

Writing Storage

To add a new value to the StorageMap, you can simply call the insert API:

#![allow(unused)]
fn main() {
let my_key: [u8; 32] = [0u8; 32];
Kitties::<T>::insert(my_key, ());
}

The same behaviors apply to StorageMap as a StorageValue.

The insert API cannot fail. If a value already exists in the map, under the key, we will simply overwrite that value. If you want to check if a value already exists in the map under a key, the most efficient way is to call contains_key(key).

Your Turn

StorageMaps are easy!

Update the logic in your pallet to insert a new kitty into your Kitties map when we call mint.

For this, you will need to add a second parameter to the mint function to pass the unique identifier for the kitty.

#![allow(unused)]
fn main() {
use super::*;
use frame::prelude::*;

impl<T: Config> Pallet<T> {
	/* 🚧 TODO 🚧: Update this function signature to include `dna` which is type `[u8; 32]`. */
	pub fn mint(owner: T::AccountId) -> DispatchResult {
		let current_count: u32 = CountForKitties::<T>::get();
		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;
		/* 🚧 TODO 🚧: In the `Kitties` map, under the key `dna`, insert `()`. */
		CountForKitties::<T>::set(new_count);
		Self::deposit_event(Event::<T>::Created { owner });
		Ok(())
	}
}
}
#![allow(unused)]
#![cfg_attr(not(feature = "std"), no_std)]

fn main() {
mod impls;
mod tests;

use frame::prelude::*;
pub use pallet::*;

#[frame::pallet(dev_mode)]
pub mod pallet {
	use super::*;

	#[pallet::pallet]
	pub struct Pallet<T>(core::marker::PhantomData<T>);

	#[pallet::config]
	pub trait Config: frame_system::Config {
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
	}

	#[pallet::storage]
	pub(super) type CountForKitties<T: Config> = StorageValue<Value = u32, QueryKind = ValueQuery>;

	#[pallet::storage]
	pub(super) type Kitties<T: Config> = StorageMap<Key = [u8; 32], Value = ()>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		Created { owner: T::AccountId },
	}

	#[pallet::error]
	pub enum Error<T> {
		TooManyKitties,
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
			let who = ensure_signed(origin)?;
			/* 🚧 TODO 🚧:
				- Create a `dna` variable for this kitty, which we will set as `[0u8; 32]` for now.
				- Pass `dna` to the `mint` function as the second parameter.
			*/
			Self::mint(who)?;
			Ok(())
		}
	}
}
}
#![allow(unused)]
fn main() {
use super::*;
use frame::prelude::*;

impl<T: Config> Pallet<T> {
	pub fn mint(owner: T::AccountId, dna: [u8; 32]) -> DispatchResult {
		let current_count: u32 = CountForKitties::<T>::get();
		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;
		Kitties::<T>::insert(dna, ());
		CountForKitties::<T>::set(new_count);
		Self::deposit_event(Event::<T>::Created { owner });
		Ok(())
	}
}
}
#![allow(unused)]
#![cfg_attr(not(feature = "std"), no_std)]

fn main() {
mod impls;
mod tests;

use frame::prelude::*;
pub use pallet::*;

#[frame::pallet(dev_mode)]
pub mod pallet {
	use super::*;

	#[pallet::pallet]
	pub struct Pallet<T>(core::marker::PhantomData<T>);

	#[pallet::config]
	pub trait Config: frame_system::Config {
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
	}

	#[pallet::storage]
	pub(super) type CountForKitties<T: Config> = StorageValue<Value = u32, QueryKind = ValueQuery>;

	#[pallet::storage]
	pub(super) type Kitties<T: Config> = StorageMap<Key = [u8; 32], Value = ()>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		Created { owner: T::AccountId },
	}

	#[pallet::error]
	pub enum Error<T> {
		TooManyKitties,
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
			let who = ensure_signed(origin)?;
			let dna = [0u8; 32];
			Self::mint(who, dna)?;
			Ok(())
		}
	}
}
}
#![allow(unused)]
fn main() {
// Tests for the Kitties Pallet.
//
// Normally this file would be split into two parts: `mock.rs` and `tests.rs`.
// The `mock.rs` file would contain all the setup code for our `TestRuntime`.
// Then `tests.rs` would only have the tests for our pallet.
// However, to minimize the project, these have been combined into this single file.
//
// Learn more about creating tests for Pallets:
// https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_docs/guides/your_first_pallet/index.html

// This flag tells rust to only run this file when running `cargo test`.
#![cfg(test)]

use crate as pallet_kitties;
use crate::*;
use frame::deps::sp_io;
use frame::runtime::prelude::*;
use frame::testing_prelude::*;
use frame::traits::fungible::*;

type Balance = u64;
type Block = frame_system::mocking::MockBlock<TestRuntime>;

// In our "test runtime", we represent a user `AccountId` with a `u64`.
// This is just a simplification so that we don't need to generate a bunch of proper cryptographic
// public keys when writing tests. It is just easier to say "user 1 transfers to user 2".
// We create the constants `ALICE` and `BOB` to make it clear when we are representing users below.
const ALICE: u64 = 1;
const BOB: u64 = 2;

// Our blockchain tests only need 3 Pallets:
// 1. System: Which is included with every FRAME runtime.
// 2. PalletBalances: Which is manages your blockchain's native currency. (i.e. DOT on Polkadot)
// 3. PalletKitties: The pallet you are building in this tutorial!
construct_runtime! {
	pub struct TestRuntime {
		System: frame_system,
		PalletBalances: pallet_balances,
		PalletKitties: pallet_kitties,
	}
}

// Normally `System` would have many more configurations, but you can see that we use some macro
// magic to automatically configure most of the pallet for a "default test configuration".
#[derive_impl(frame_system::config_preludes::TestDefaultConfig)]
impl frame_system::Config for TestRuntime {
	type Block = Block;
	type AccountData = pallet_balances::AccountData<Balance>;
}

// Normally `pallet_balances` would have many more configurations, but you can see that we use some
// macro magic to automatically configure most of the pallet for a "default test configuration".
#[derive_impl(pallet_balances::config_preludes::TestDefaultConfig)]
impl pallet_balances::Config for TestRuntime {
	type AccountStore = System;
	type Balance = Balance;
}

// This is the configuration of our Pallet! If you make changes to the pallet's `trait Config`, you
// will also need to update this configuration to represent that.
impl pallet_kitties::Config for TestRuntime {
	type RuntimeEvent = RuntimeEvent;
}

// We need to run most of our tests using this function: `new_test_ext().execute_with(|| { ... });`
// It simulates the blockchain database backend for our tests.
// If you forget to include this and try to access your Pallet storage, you will get an error like:
// "`get_version_1` called outside of an Externalities-provided environment."
pub fn new_test_ext() -> sp_io::TestExternalities {
	frame_system::GenesisConfig::<TestRuntime>::default()
		.build_storage()
		.unwrap()
		.into()
}

#[test]
fn starting_template_is_sane() {
	new_test_ext().execute_with(|| {
		let event = Event::<TestRuntime>::Created { owner: ALICE };
		let _runtime_event: RuntimeEvent = event.into();
		let _call = Call::<TestRuntime>::create_kitty {};
		let result = PalletKitties::create_kitty(RuntimeOrigin::signed(BOB));
		assert_ok!(result);
	});
}

#[test]
fn system_and_balances_work() {
	// This test will just sanity check that we can access `System` and `PalletBalances`.
	new_test_ext().execute_with(|| {
		// We often need to set `System` to block 1 so that we can see events.
		System::set_block_number(1);
		// We often need to add some balance to a user to test features which needs tokens.
		assert_ok!(PalletBalances::mint_into(&ALICE, 100));
		assert_ok!(PalletBalances::mint_into(&BOB, 100));
	});
}

#[test]
fn create_kitty_checks_signed() {
	new_test_ext().execute_with(|| {
		// The `create_kitty` extrinsic should work when being called by a user.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// The `create_kitty` extrinsic should fail when being called by an unsigned message.
		assert_noop!(PalletKitties::create_kitty(RuntimeOrigin::none()), DispatchError::BadOrigin);
	})
}

#[test]
fn create_kitty_emits_event() {
	new_test_ext().execute_with(|| {
		// We need to set block number to 1 to view events.
		System::set_block_number(1);
		// Execute our call, and ensure it is successful.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Assert the last event by our blockchain is the `Created` event with the correct owner.
		System::assert_last_event(Event::<TestRuntime>::Created { owner: 1 }.into());
	})
}

#[test]
fn count_for_kitties_created_correctly() {
	new_test_ext().execute_with(|| {
		// Querying storage before anything is set will return `0`.
		assert_eq!(CountForKitties::<TestRuntime>::get(), 0);
		// You can `set` the value using an `u32`.
		CountForKitties::<TestRuntime>::set(1337u32);
		// You can `put` the value directly with a `u32`.
		CountForKitties::<TestRuntime>::put(1337u32);
	})
}

#[test]
fn mint_increments_count_for_kitty() {
	new_test_ext().execute_with(|| {
		// Querying storage before anything is set will return `0`.
		assert_eq!(CountForKitties::<TestRuntime>::get(), 0);
		// Call `create_kitty` which will call `mint`.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Now the storage should be `1`
		assert_eq!(CountForKitties::<TestRuntime>::get(), 1);
	})
}

#[test]
fn mint_errors_when_overflow() {
	new_test_ext().execute_with(|| {
		// Set the count to the largest value possible.
		CountForKitties::<TestRuntime>::set(u32::MAX);
		// `create_kitty` should not succeed because of safe math.
		assert_noop!(
			PalletKitties::create_kitty(RuntimeOrigin::signed(1)),
			Error::<TestRuntime>::TooManyKitties
		);
	})
}

#[test]
fn kitties_map_created_correctly() {
	new_test_ext().execute_with(|| {
		let zero_key = [0u8; 32];
		assert!(!Kitties::<TestRuntime>::contains_key(zero_key));
		Kitties::<TestRuntime>::insert(zero_key, ());
		assert!(Kitties::<TestRuntime>::contains_key(zero_key));
	})
}

#[test]
fn create_kitty_adds_to_map() {
	new_test_ext().execute_with(|| {
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		assert_eq!(Kitties::<TestRuntime>::iter().count(), 1);
	})
}
}
diff --git a/src/impls.rs b/src/impls.rs
index d283fd6..4443702 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -2,9 +2,11 @@ use super::*;
 use frame::prelude::*;
 
 impl<T: Config> Pallet<T> {
+	/* 🚧 TODO 🚧: Update this function signature to include `dna` which is type `[u8; 32]`. */
 	pub fn mint(owner: T::AccountId) -> DispatchResult {
 		let current_count: u32 = CountForKitties::<T>::get();
 		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;
+		/* 🚧 TODO 🚧: In the `Kitties` map, under the key `dna`, insert `()`. */
 		CountForKitties::<T>::set(new_count);
 		Self::deposit_event(Event::<T>::Created { owner });
 		Ok(())
diff --git a/src/lib.rs b/src/lib.rs
index 42fb376..717c900 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,6 +39,10 @@ pub mod pallet {
 	impl<T: Config> Pallet<T> {
 		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
 			let who = ensure_signed(origin)?;
+			/* 🚧 TODO 🚧:
+				- Create a `dna` variable for this kitty, which we will set as `[0u8; 32]` for now.
+				- Pass `dna` to the `mint` function as the second parameter.
+			*/
 			Self::mint(who)?;
 			Ok(())
 		}
diff --git a/src/impls.rs b/src/impls.rs
index 4443702..363f5e4 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -2,11 +2,10 @@ use super::*;
 use frame::prelude::*;
 
 impl<T: Config> Pallet<T> {
-	/* 🚧 TODO 🚧: Update this function signature to include `dna` which is type `[u8; 32]`. */
-	pub fn mint(owner: T::AccountId) -> DispatchResult {
+	pub fn mint(owner: T::AccountId, dna: [u8; 32]) -> DispatchResult {
 		let current_count: u32 = CountForKitties::<T>::get();
 		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;
-		/* 🚧 TODO 🚧: In the `Kitties` map, under the key `dna`, insert `()`. */
+		Kitties::<T>::insert(dna, ());
 		CountForKitties::<T>::set(new_count);
 		Self::deposit_event(Event::<T>::Created { owner });
 		Ok(())
diff --git a/src/lib.rs b/src/lib.rs
index 717c900..15fb504 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,11 +39,8 @@ pub mod pallet {
 	impl<T: Config> Pallet<T> {
 		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
 			let who = ensure_signed(origin)?;
-			/* 🚧 TODO 🚧:
-				- Create a `dna` variable for this kitty, which we will set as `[0u8; 32]` for now.
-				- Pass `dna` to the `mint` function as the second parameter.
-			*/
-			Self::mint(who)?;
+			let dna = [0u8; 32];
+			Self::mint(who, dna)?;
 			Ok(())
 		}
 	}
diff --git a/src/tests.rs b/src/tests.rs
index 9899cf0..bd4bf55 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -164,3 +164,11 @@ fn kitties_map_created_correctly() {
 		assert!(Kitties::<TestRuntime>::contains_key(zero_key));
 	})
 }
+
+#[test]
+fn create_kitty_adds_to_map() {
+	new_test_ext().execute_with(|| {
+		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
+		assert_eq!(Kitties::<TestRuntime>::iter().count(), 1);
+	})
+}