[Feat/#17] TodoViewModel의 핀 토글 기능을 구현한다

DevLog/Data/Protocol/Dictionaryable.swift

@@ -5,19 +5,31 @@
 //  Created by 최윤진 on 12/14/25.
 //
 
-import Foundation
+import FirebaseFirestore
 
 protocol Dictionaryable: Encodable {
     func toDictionary() -> [String: Any]
 }
 
 extension Dictionaryable {
     func toDictionary() -> [String: Any] {
-        guard let encodedData = try? JSONEncoder().encode(self),
-              var dictionary = (try? JSONSerialization.jsonObject(with: encodedData)) as? [String: Any]
-        else { return [:] }
+        let encoder = Firestore.Encoder()
+        guard var dictionary = try? encoder.encode(self) else { return [:] }
+
+        let mirror = Mirror(reflecting: self)
+        for child in mirror.children {
+            guard let key = child.label else { continue }
+            if isNilValue(child.value) {
+                dictionary[key] = NSNull()
+            }
+        }
 
         dictionary.removeValue(forKey: "id")
         return dictionary
     }
+
+    private func isNilValue(_ value: Any) -> Bool {
+        let mirror = Mirror(reflecting: value)
+        return mirror.displayStyle == .optional && mirror.children.isEmpty
+    }
 }

DevLog/Presentation/ViewModel/TodoViewModel.swift

@@ -131,7 +131,18 @@ final class TodoViewModel: Store {
                 }
             }
         case .togglePinned(let todo):
-            break
+            Task {
+                do {
+                    defer { send(.didLoading(false)) }
+                    send(.didLoading(true))
+                    var todo = todo
+                    todo.isPinned.toggle()
+                    try await upsertTodoUseCase.execute(todo)
+                    send(.didTogglePinned(todo))
+                } catch {
+                    send(.didShowAlert(error.localizedDescription))
+                }
+            }
         case .swipeTodo(let todo):
             break
         }