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//
// Copyright © 2019 Swinject Contributors. All rights reserved.
//
/// Storage provided by `ObjectScope`. It is used by `Container` to persist resolved instances.
public protocol InstanceStorage: AnyObject {
var instance: Any? { get set }
func graphResolutionCompleted()
func instance(inGraph graph: GraphIdentifier) -> Any?
func setInstance(_ instance: Any?, inGraph graph: GraphIdentifier)
}
extension InstanceStorage {
public func graphResolutionCompleted() {}
public func instance(inGraph _: GraphIdentifier) -> Any? { return instance }
public func setInstance(_ instance: Any?, inGraph _: GraphIdentifier) { self.instance = instance }
}
/// Persists storage during the resolution of the object graph
public final class GraphStorage: InstanceStorage {
private var instances = [GraphIdentifier: Weak<Any>]()
public var instance: Any?
public init() {}
public func graphResolutionCompleted() {
instance = nil
}
public func instance(inGraph graph: GraphIdentifier) -> Any? {
return instances[graph]?.value
}
public func setInstance(_ instance: Any?, inGraph graph: GraphIdentifier) {
self.instance = instance
if instances[graph] == nil { instances[graph] = Weak() }
instances[graph]?.value = instance
}
}
/// Persists stored instance until it is explicitly discarded.
public final class PermanentStorage: InstanceStorage {
public var instance: Any?
public init() {}
}
/// Does not persist stored instance.
public final class TransientStorage: InstanceStorage {
public var instance: Any? {
get { return nil }
set {} // swiftlint:disable:this unused_setter_value
}
public init() {}
}
/// Does not persist value types.
/// Persists reference types as long as there are strong references to given instance.
public final class WeakStorage: InstanceStorage {
private var _instance = Weak<Any>()
public var instance: Any? {
get { return _instance.value }
set { _instance.value = newValue }
}
public init() {}
}
/// Combines the behavior of multiple instance storages.
/// Instance is persisted as long as at least one of the underlying storages is persisting it.
public final class CompositeStorage: InstanceStorage {
private let components: [InstanceStorage]
public var instance: Any? {
get {
#if swift(>=4.1)
return components.compactMap { $0.instance }.first
#else
return components.flatMap { $0.instance }.first
#endif
}
set { components.forEach { $0.instance = newValue } }
}
public init(_ components: [InstanceStorage]) {
self.components = components
}
public func graphResolutionCompleted() {
components.forEach { $0.graphResolutionCompleted() }
}
public func setInstance(_ instance: Any?, inGraph graph: GraphIdentifier) {
components.forEach { $0.setInstance(instance, inGraph: graph) }
}
public func instance(inGraph graph: GraphIdentifier) -> Any? {
#if swift(>=4.1)
return components.compactMap { $0.instance(inGraph: graph) }.first
#else
return components.flatMap { $0.instance(inGraph: graph) }.first
#endif
}
}
private class Weak<Wrapped> {
private weak var object: AnyObject?
#if os(Linux)
var value: Wrapped? {
get {
guard let object = object else { return nil }
return object as? Wrapped
}
set { object = newValue.flatMap { $0 as? AnyObject } }
}
#else
var value: Wrapped? {
get {
guard let object = object else { return nil }
return object as? Wrapped
}
set { object = newValue as AnyObject? }
}
#endif
}