Be able to set nil values

Sources/Reflection/Any+Extensions.swift

@@ -22,7 +22,7 @@ extension AnyExtensions {
         return storage.assumingMemoryBound(to: self).pointee
     }
 
-    static func write(_ value: Any, to storage: UnsafeMutableRawPointer) throws {
+    static func write(_ value: Any?, to storage: UnsafeMutableRawPointer) throws {
         guard let this = value as? Self else {
             throw ReflectionError.valueIsNotType(value: value, type: self)
         }

Sources/Reflection/Properties.swift

@@ -24,7 +24,7 @@ public struct Property {
         public let key: String
         public let type: Any.Type
         let offset: Int
-        func write(_ value: Any, to storage: UnsafeMutableRawPointer) throws {
+        func write(_ value: Any?, to storage: UnsafeMutableRawPointer) throws {
             return try extensions(of: type).write(value, to: storage.advanced(by: offset))
         }
     }

Sources/Reflection/ReflectionError.swift

@@ -1,6 +1,6 @@
 public enum ReflectionError : Error, CustomStringConvertible, Equatable {
     case notStruct(type: Any.Type)
-    case valueIsNotType(value: Any, type: Any.Type)
+    case valueIsNotType(value: Any?, type: Any.Type)
     case instanceHasNoKey(type: Any.Type, key: String)
     case requiredValueMissing(key: String)
     case unexpected

Sources/Reflection/Set.swift

@@ -1,17 +1,17 @@
 /// Set value for key of an instance
-public func set(_ value: Any, key: String, for instance: inout Any) throws {
+public func set(_ value: Any?, key: String, for instance: inout Any) throws {
     let type = Swift.type(of: instance)
     try property(type: type, key: key).write(value, to: mutableStorage(instance: &instance, type: type))
 }
 
 /// Set value for key of an instance
-public func set(_ value: Any, key: String, for instance: AnyObject) throws {
+public func set(_ value: Any?, key: String, for instance: AnyObject) throws {
     var copy: Any = instance
     try set(value, key: key, for: &copy)
 }
 
 /// Set value for key of an instance
-public func set<T>(_ value: Any, key: String, for instance: inout T) throws {
+public func set<T>(_ value: Any?, key: String, for instance: inout T) throws {
     try property(type: T.self, key: key).write(value, to: mutableStorage(instance: &instance))
 }
 

Tests/ReflectionTests/PublicTests.swift

@@ -2,9 +2,9 @@ import XCTest
 import Reflection
 
 struct Person : Equatable {
-    var firstName: String
+    var firstName: String?
     var lastName: String
-    var age: Int
+    var age: Int?
 
     init(firstName: String, lastName: String, age: Int) {
         self.firstName = firstName
@@ -133,7 +133,14 @@ public class PublicTests : XCTestCase {
     func testSetValueForKeyOfInstance() throws {
         var person = Person(firstName: "Brad", lastName: "Hilton", age: 27)
         try set("Lawrence", key: "firstName", for: &person)
-        XCTAssert(person.firstName == "Lawrence")
+        XCTAssertEqual(person.firstName, "Lawrence")
+        try set(nil, key: "firstName", for: &person)
+        XCTAssertNil(person.firstName)
+        XCTAssertEqual(person.age, 27)
+        try set(nil, key: "age", for: &person)
+        XCTAssertNil(person.age)
+        try set(28, key: "age", for: &person)
+        XCTAssertEqual(person.age, 28)
     }
 
     func testValueForKeyOfInstance() throws {
@@ -204,9 +211,7 @@ public class PublicTests : XCTestCase {
             XCTFail()
         } catch let constructionErrors as ConstructionErrors {
             let expectedErrors: [ReflectionError] = [
-                .requiredValueMissing(key: "firstName"),
                 .requiredValueMissing(key: "lastName"),
-                .requiredValueMissing(key: "age")
             ]
             XCTAssertEqual(constructionErrors.errors.compactMap { $0 as? ReflectionError }, expectedErrors)
         } catch {