Introduce single

Sources/FirebladeECS/Nexus+Entity.swift

@@ -13,15 +13,18 @@ extension Nexus {
 		return nextReused.index
 	}
 
-	public func create(entity name: String? = nil) -> Entity {
+    // swiftlint:disable function_default_parameter_at_end
+	@discardableResult
+     public func create(entity name: String? = nil, with assignedComponents: Component...) -> Entity {
 		let newEntityIndex: EntityIndex = nextEntityIdx()
 		let newEntityIdentifier: EntityIdentifier = newEntityIndex.identifier
-
         let newEntity = Entity(nexus: self, id: newEntityIdentifier, name: name)
 		entityStorage.insert(newEntity, at: newEntityIndex)
 		notify(EntityCreated(entityId: newEntityIdentifier))
+        assignedComponents.forEach { newEntity.assign($0) }
         return newEntity
     }
+    // swiftlint:enable function_default_parameter_at_end
 
 	/// Number of entities in nexus.
 	public var numEntities: Int {

Sources/FirebladeECS/Nexus+TypedSingle.swift

@@ -0,0 +1,19 @@
+//
+//  Nexus+TypedSingle.swift
+//  FirebladeECS
+//
+//  Created by Christian Treffs on 13.02.19.
+//
+
+public extension Nexus {
+    func single<A>(
+        requires componentA: A.Type,
+        excludesAll excludedComponents: Component.Type...
+        ) -> TypedSingle1<A> where A: Component {
+        return TypedSingle1(
+            self,
+            requires: componentA,
+            excludesAll: excludedComponents
+        )
+    }
+}

Sources/FirebladeECS/TypedSingle.swift

@@ -0,0 +1,38 @@
+//
+//  TypedSingle.swift
+//  FirebladeECS
+//
+//  Created by Christian Treffs on 13.02.19.
+//
+
+public struct TypedSingle1<A>: Equatable where A: Component {
+    public let nexus: Nexus
+    public let traits: FamilyTraitSet
+
+    public init(_ nexus: Nexus, requires compA: A.Type, excludesAll: [Component.Type]) {
+        self.nexus = nexus
+        traits = FamilyTraitSet(requiresAll: [compA], excludesAll: excludesAll)
+        nexus.onFamilyInit(traits: traits)
+    }
+
+    @inlinable public var entityId: EntityIdentifier? {
+        guard let members = nexus.members(withFamilyTraits: traits) else {
+            return nil
+        }
+        guard let singleMemberId: EntityIdentifier = members.first else {
+            return nil
+        }
+        return singleMemberId
+    }
+
+    @inlinable public var entity: Entity? {
+        guard let entityId = entityId else {
+            return nil
+        }
+        return nexus.get(entity: entityId)
+    }
+
+    @inlinable public var component: A? {
+        return entity?.get(component: A.self)
+    }
+}

Tests/FirebladeECSTests/SingleTests.swift

@@ -0,0 +1,67 @@
+//
+//  SingleTests.swift
+//  FirebladeECSTests
+//
+//  Created by Christian Treffs on 13.02.19.
+//
+
+
+@testable import FirebladeECS
+import XCTest
+
+class SingleTests: XCTestCase {
+    var nexus: Nexus!
+    
+    override func setUp() {
+        super.setUp()
+        nexus = Nexus()
+    }
+    
+    override func tearDown() {
+        nexus = nil
+        super.tearDown()
+    }
+    
+    func testSingleCreation() {
+        let single = nexus.single(requires: Position.self,
+                                  excludesAll: Name.self)
+        XCTAssertEqual(single.nexus, self.nexus)
+        XCTAssertTrue(single.nexus === self.nexus)
+        XCTAssertEqual(single.traits.requiresAll.count, 1)
+        XCTAssertEqual(single.traits.excludesAll.count, 1)
+        
+        XCTAssertEqual(nexus.familyMembersByTraits.keys.count, 1)
+        XCTAssertEqual(nexus.familyMembersByTraits.values.count, 1)
+        
+        let traits = FamilyTraitSet(requiresAll: [Position.self], excludesAll: [Name.self])
+        XCTAssertEqual(single.traits, traits)
+    }
+    
+    func testSingleReuse() {
+        let singleA = nexus.single(requires: Position.self,
+                                   excludesAll: Name.self)
+        
+        let singleB = nexus.single(requires: Position.self,
+                                   excludesAll: Name.self)
+        
+        XCTAssertEqual(nexus.familyMembersByTraits.keys.count, 1)
+        XCTAssertEqual(nexus.familyMembersByTraits.values.count, 1)
+        
+        XCTAssertEqual(singleA, singleB)
+    }
+    
+    
+    func testSingleEntityAndComponentCreation() {
+        let single = nexus.single(requires: Position.self,
+                                  excludesAll: Name.self)
+        XCTAssertNil(single.entity)
+        XCTAssertNil(single.component)
+        let pos = Position(x: 1, y: 2)
+        nexus.create(with: pos)
+        XCTAssertNotNil(single.entity)
+        XCTAssertNotNil(single.component)
+        XCTAssertEqual(single.component?.x, pos.x)
+        XCTAssertEqual(single.component?.y, pos.y)
+        
+    }
+}