Add nonfungibles::Create Trait & Implement for Uniques (#9438)

* Add nonfungibles::Create Trait & Implement for Uniques

Closes #9419

* Formatting

* Remove default implementation (`TokenError::Unsupported`) from `Create` trait

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Formatting

* Do not wrap parameters in Options

* Formatting

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/support/src/traits/tokens/nonfungibles.rs

@@ -117,6 +117,12 @@ pub trait InspectEnumerable<AccountId>: Inspect<AccountId> {
 	) -> Box<dyn Iterator<Item = Self::InstanceId>>;
 }
 
+/// Trait for providing the ability to create classes of nonfungible assets.
+pub trait Create<AccountId>: Inspect<AccountId> {
+	/// Create a `class` of nonfungible assets to be owned by `who` and managed by `admin`.
+	fn create_class(class: &Self::ClassId, who: &AccountId, admin: &AccountId) -> DispatchResult;
+}
+
 /// Trait for providing an interface for multiple classes of NFT-like assets which may be minted,
 /// burned and/or have attributes set on them.
 pub trait Mutate<AccountId>: Inspect<AccountId> {

substrate/frame/uniques/src/functions.rs

@@ -48,6 +48,38 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		Ok(())
 	}
 
+	pub(super) fn do_create_class(
+		class: T::ClassId,
+		owner: T::AccountId,
+		admin: T::AccountId,
+		deposit: DepositBalanceOf<T, I>,
+		free_holding: bool,
+		event: Event<T, I>,
+	) -> DispatchResult {
+		ensure!(!Class::<T, I>::contains_key(class), Error::<T, I>::InUse);
+
+		T::Currency::reserve(&owner, deposit)?;
+
+		Class::<T, I>::insert(
+			class,
+			ClassDetails {
+				owner: owner.clone(),
+				issuer: admin.clone(),
+				admin: admin.clone(),
+				freezer: admin.clone(),
+				total_deposit: deposit,
+				free_holding,
+				instances: 0,
+				instance_metadatas: 0,
+				attributes: 0,
+				is_frozen: false,
+			},
+		);
+
+		Self::deposit_event(event);
+		Ok(())
+	}
+
 	pub(super) fn do_mint(
 		class: T::ClassId,
 		instance: T::InstanceId,

substrate/frame/uniques/src/impl_nonfungibles.rs

@@ -19,7 +19,10 @@
 
 use super::*;
 use frame_support::{
-	traits::tokens::nonfungibles::{Inspect, InspectEnumerable, Mutate, Transfer},
+	traits::{
+		tokens::nonfungibles::{Create, Inspect, InspectEnumerable, Mutate, Transfer},
+		Get,
+	},
 	BoundedSlice,
 };
 use sp_runtime::DispatchResult;
@@ -85,6 +88,24 @@ impl<T: Config<I>, I: 'static> Inspect<<T as SystemConfig>::AccountId> for Palle
 	}
 }
 
+impl<T: Config<I>, I: 'static> Create<<T as SystemConfig>::AccountId> for Pallet<T, I> {
+	/// Create a `class` of nonfungible assets to be owned by `who` and managed by `admin`.
+	fn create_class(
+		class: &Self::ClassId,
+		who: &T::AccountId,
+		admin: &T::AccountId,
+	) -> DispatchResult {
+		Self::do_create_class(
+			class.clone(),
+			who.clone(),
+			admin.clone(),
+			T::ClassDeposit::get(),
+			false,
+			Event::Created(class.clone(), who.clone(), admin.clone()),
+		)
+	}
+}
+
 impl<T: Config<I>, I: 'static> Mutate<<T as SystemConfig>::AccountId> for Pallet<T, I> {
 	fn mint_into(
 		class: &Self::ClassId,

substrate/frame/uniques/src/lib.rs

@@ -316,28 +316,14 @@ pub mod pallet {
 			let owner = ensure_signed(origin)?;
 			let admin = T::Lookup::lookup(admin)?;
 
-			ensure!(!Class::<T, I>::contains_key(class), Error::<T, I>::InUse);
+			Self::do_create_class(
-
-			let deposit = T::ClassDeposit::get();
-			T::Currency::reserve(&owner, deposit)?;
-
-			Class::<T, I>::insert(
 				class,
-				ClassDetails {
+				owner.clone(),
-					owner: owner.clone(),
+				admin.clone(),
-					issuer: admin.clone(),
+				T::ClassDeposit::get(),
-					admin: admin.clone(),
+				false,
-					freezer: admin.clone(),
+				Event::Created(class, owner, admin),
-					total_deposit: deposit,
+			)
-					free_holding: false,
-					instances: 0,
-					instance_metadatas: 0,
-					attributes: 0,
-					is_frozen: false,
-				},
-			);
-			Self::deposit_event(Event::Created(class, owner, admin));
-			Ok(())
 		}
 
 		/// Issue a new class of non-fungible assets from a privileged origin.
@@ -366,25 +352,14 @@ pub mod pallet {
 			T::ForceOrigin::ensure_origin(origin)?;
 			let owner = T::Lookup::lookup(owner)?;
 
-			ensure!(!Class::<T, I>::contains_key(class), Error::<T, I>::InUse);
+			Self::do_create_class(
-
-			Class::<T, I>::insert(
 				class,
-				ClassDetails {
+				owner.clone(),
-					owner: owner.clone(),
+				owner.clone(),
-					issuer: owner.clone(),
+				Zero::zero(),
-					admin: owner.clone(),
+				free_holding,
-					freezer: owner.clone(),
+				Event::ForceCreated(class, owner),
-					total_deposit: Zero::zero(),
+			)
-					free_holding,
-					instances: 0,
-					instance_metadatas: 0,
-					attributes: 0,
-					is_frozen: false,
-				},
-			);
-			Self::deposit_event(Event::ForceCreated(class, owner));
-			Ok(())
 		}
 
 		/// Destroy a class of fungible assets.