Added WeakLazyInjected property wrapper for parent child relationships

CHANGELOG

@@ -1,5 +1,9 @@
 # Factory Changelog
 
+### 1.2.5
+
+* Added WeakLazyInjected property wrapper for parent child relationships
+
 ### 1.2.4
 
 * Recursive lock required in scope resolution

README.md

@@ -281,6 +281,37 @@ Next, note that Factory is *thread-safe.* Registrations and resolutions lock and
 
 And finally, note that calling register also *removes any cached dependency from its associated scope.* This ensures that any new dependency injection request performed from that point on will always get the most recently defined instance of an object.
 
+## Lazy and Weak Injections
+Factory also has `LazyInjected` and `WeakLazyInjected` property wrappers. Use `LazyInjected` when you want to defer construction of some class until it's actually needed. Here the child `service` won't be instantiated until the `test` function is called.
+```
+class ServicesP {
+    @LazyInjected(Container.servicesC) var service
+    let name = "Parent"
+    init() {}
+    func test() -> String? {
+        service.name
+    }
+}
+```
+And `WeakLazyInjected` is useful when building parent/child relationships and you want to avoid retain cycles back to the parent class. It's also lazy since otherwise you'd have a cyclic dependency between the parent and the child. (P needs C which needs P which needs C which...)'
+```swift
+class ServicesC {
+    @WeakLazyInjected(Container.servicesP) var service: ServicesP?
+    init() {}
+    let name = "Child"
+    func test() -> String? {
+        service?.name
+    }
+}
+```
+And the factories. Note the shared scopes so references can be kept and maintained for the parent/child relationships.
+```swift
+extension Container {
+    static var servicesP = Factory(scope: .shared) { ServicesP() }
+    static var servicesC = Factory(scope: .shared) { ServicesC() }
+}
+```
+
 ## Custom Containers
 
 In a large project you might want to segregate factories into additional, smaller containers.

Sources/Factory/Factory.swift

@@ -306,15 +306,36 @@ extension SharedContainer.Scope {
 @propertyWrapper public struct LazyInjected<T> {
     private var factory: Factory<T>
     private var dependency: T!
-    private var injectionNeeded = true
+    private var initialize = true
     public init(_ factory: Factory<T>) {
         self.factory = factory
     }
     public var wrappedValue: T {
         mutating get {
-            if injectionNeeded {
+            if initialize {
                 dependency = factory()
-                injectionNeeded = false
+                initialize = false
+            }
+            return dependency
+        }
+        mutating set {
+            dependency = newValue
+        }
+    }
+}
+
+@propertyWrapper public struct WeakLazyInjected<T:AnyObject> {
+    private var factory: Factory<T>
+    private weak var dependency: T?
+    private var initialize = true
+    public init(_ factory: Factory<T>) {
+        self.factory = factory
+    }
+    public var wrappedValue: T? {
+        mutating get {
+            if initialize {
+                dependency = factory()
+                initialize = false
             }
             return dependency
         }

Tests/FactoryTests/FactoryInjectionTests.swift

@@ -18,6 +18,30 @@ class Services5 {
     init() {}
 }
 
+class ServicesP {
+    @LazyInjected(Container.servicesC) var service
+    let name = "Parent"
+    init() {}
+    func test() -> String? {
+        service.name
+    }
+}
+
+class ServicesC {
+    @WeakLazyInjected(Container.servicesP) var service: ServicesP?
+    init() {}
+    let name = "Child"
+    func test() -> String? {
+        service?.name
+    }
+}
+
+extension Container {
+    fileprivate static var servicesP = Factory(scope: .shared) { ServicesP() }
+    fileprivate static var servicesC = Factory(scope: .shared) { ServicesC() }
+}
+
+
 final class FactoryInjectionTests: XCTestCase {
 
     override func setUp() {
@@ -50,4 +74,13 @@ final class FactoryInjectionTests: XCTestCase {
         XCTAssertTrue(services.service?.text() == "MyService")
     }
 
+    func testWeakLazyInjection() throws {
+        var parent: ServicesP? = Container.servicesP()
+        let child = Container.servicesC()
+        XCTAssertTrue(parent?.test() == "Child")
+        XCTAssertTrue(child.test() == "Parent")
+        parent = nil
+        XCTAssertNil(child.test())
+    }
+
 }