52 lines
1.6 KiB
Swift
52 lines
1.6 KiB
Swift
//
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// Single.swift
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// FirebladeECS
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//
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// Created by Christian Treffs on 13.02.19.
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//
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public protocol SingleComponent: Component {
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init()
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}
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public struct Single<A> where A: SingleComponent {
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public let nexus: Nexus
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public let traits: FamilyTraitSet
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public let entityId: EntityIdentifier
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}
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extension Single: Equatable {
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public static func == (lhs: Single<A>, rhs: Single<A>) -> Bool {
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lhs.traits == rhs.traits &&
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lhs.entityId == rhs.entityId &&
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lhs.nexus === rhs.nexus
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}
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}
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extension Single where A: SingleComponent {
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@inlinable public var component: A {
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// Since we guarantee that the component will always be present by managing the complete lifecycle of the entity
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// and component assignment we may unsafelyUnwrap here.
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// Since components will always be of reference type (class) we may use unsafeDowncast here for performance reasons.
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nexus.get(unsafe: entityId)
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}
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public var entity: Entity {
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Entity(nexus: nexus, id: entityId)
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}
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}
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extension Nexus {
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public func single<S>(_ component: S.Type) -> Single<S> where S: SingleComponent {
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let family = self.family(requires: S.self)
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precondition(family.count <= 1, "Singleton count of \(S.self) must be 0 or 1: \(family.count)")
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let entityId: EntityIdentifier
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if family.isEmpty {
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entityId = createEntity(with: S()).identifier
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} else {
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entityId = family.memberIds.first.unsafelyUnwrapped
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}
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return Single<S>(nexus: self, traits: family.traits, entityId: entityId)
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}
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}
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