Merge pull request #38 from petermajor/master

Add @OptionalInjected attribute

Author: hmlongco

Documentation/Annotation.md

@@ -56,6 +56,18 @@ class NamedInjectedViewController: UIViewController {
 ```
 If you go this route just make sure you specify the name *before* accessing the injected service for the first time.
 
+###  Optional injection
+
+An annotation is available that supports optional resolving. If the service is not registered, then the value will be nil, otherwise it will be not nil:
+```
+class InjectedViewController: UIViewController {
+    @OptionalInjected var service: XYZService?
+    func load() {
+        service?.load()
+    }
+}
+```
+
 ### Custom Containers
 
 You can specify and resolve custom containers using Injected. Just define your custom container...

Documentation/Optionals.md

@@ -54,3 +54,15 @@ This could be helpful if for some reason you wanted to resolve to a specific ins
 ```swift
 var abc: ABCServicing? = Resolver.resolve(ABCService.self)
 ```
+
+##  Optional annotation
+
+An annotation is available that supports optional resolving. If the service is not registered, then the value will be nil, otherwise it will be not nil:
+```
+class InjectedViewController: UIViewController {
+    @OptionalInjected var service: XYZService?
+    func load() {
+        service?.load()
+    }
+}
+```

Sources/Resolver/Resolver.swift

@@ -625,6 +625,25 @@ public struct LazyInjected<Service> {
     }
 }
 
+@propertyWrapper
+public struct OptionalInjected<Service> {
+    private var service: Service?
+    public init() {
+        self.service = Resolver.optional(Service.self)
+    }
+    public init(name: String? = nil, container: Resolver? = nil) {
+        self.service = container?.optional(Service.self, name: name) ?? Resolver.optional(Service.self, name: name)
+    }
+    public var wrappedValue: Service? {
+        get { return service }
+        mutating set { service = newValue }
+    }
+    public var projectedValue: OptionalInjected<Service> {
+        get { return self }
+        mutating set { self = newValue }
+    }
+}
+
 /// Immediate injection property wrapper for SwiftUI ObservableObjects. This wrapper is meant for use in SwiftUI Views and exposes
 /// bindable objects similar to that of SwiftUI @observedObject and @environmentObject.
 ///

Tests/ResolverTests/ResolverInjectedTests.swift

@@ -35,6 +35,14 @@ class LazyInjectedViewController {
     @LazyInjected var service: XYZService
 }
 
+class OptionalInjectedViewController {
+    @OptionalInjected var service: XYZService?
+    @OptionalInjected var notRegistered: NotRegistered?
+}
+
+class NotRegistered {
+}
+
 class ResolverInjectedTests: XCTestCase {
 
     override func setUp() {
@@ -84,7 +92,12 @@ class ResolverInjectedTests: XCTestCase {
         XCTAssertNotNil(vc.service.session)
         XCTAssert(!vc.$service.isEmpty)
     }
-
+    
+    func testOptionalInjection() {
+        let vc = OptionalInjectedViewController()
+        XCTAssertNotNil(vc.service)
+        XCTAssertNil(vc.notRegistered)
+    }
 }
 
 #endif