Merge pull request #33 from fireblade-engine/feature/entity-iterator

EntitiesIterator

Sources/FirebladeECS/Entity.swift

@@ -133,6 +133,7 @@ extension Entity {
         }
     }
 }
+extension Entity.ComponentsIterator: Sequence { }
 
 extension Entity: Equatable {
     public static func == (lhs: Entity, rhs: Entity) -> Bool {

Sources/FirebladeECS/Nexus+Entity.swift

@@ -33,6 +33,13 @@ extension Nexus {
         componentIdsByEntity.keys.count
     }
 
+    /// Creates an iterator over all entities in the nexus.
+    ///
+    /// Entity order is not guaranteed to stay the same over iterations.
+    public func makeEntitiesIterator() -> EntitiesIterator {
+        EntitiesIterator(nexus: self)
+    }
+
     public func exists(entity entityId: EntityIdentifier) -> Bool {
         componentIdsByEntity.keys.contains(entityId)
     }
@@ -67,3 +74,26 @@ extension Nexus {
         return true
     }
 }
+
+// MARK: - entities iterator
+extension Nexus {
+    public struct EntitiesIterator: IteratorProtocol {
+        private var iterator: AnyIterator<Entity>
+
+        @usableFromInline
+        init(nexus: Nexus) {
+            var iter = nexus.componentIdsByEntity.keys.makeIterator()
+            iterator = AnyIterator {
+                guard let entityId = iter.next() else {
+                    return nil
+                }
+                return Entity(nexus: nexus, id: entityId)
+            }
+        }
+
+        public func next() -> Entity? {
+            iterator.next()
+        }
+    }
+}
+extension Nexus.EntitiesIterator: Sequence { }

Tests/FirebladeECSTests/NexusTests.swift

@@ -155,4 +155,15 @@ class NexusTests: XCTestCase {
         XCTAssert(pB.x != pA.x)
         XCTAssert(pB.y != pA.y)
     }
+
+    func testEntityIteration() {
+        nexus.createEntities(count: 1000) { ctx in Position(x: ctx.index, y: ctx.index) }
+
+        let entityArray = [Entity](nexus.makeEntitiesIterator()).lazy
+
+        XCTAssertEqual(entityArray.count, 1000)
+
+        XCTAssertTrue(entityArray.contains(where: { $0.identifier.index == 0 }))
+        XCTAssertTrue(entityArray.contains(where: { $0.identifier.index == 999 }))
+    }
 }

Tests/FirebladeECSTests/XCTestManifests.swift

@@ -342,7 +342,8 @@ extension NexusTests {
         ("testComponentRetrieval", testComponentRetrieval),
         ("testComponentUniqueness", testComponentUniqueness),
         ("testEntityCreate", testEntityCreate),
-        ("testEntityDestroy", testEntityDestroy)
+        ("testEntityDestroy", testEntityDestroy),
+        ("testEntityIteration", testEntityIteration)
     ]
 }