diff --git a/Source/Modules/ControllerModules/InputState.swift b/Source/Modules/ControllerModules/InputState.swift
index f03ecda2..c262c933 100644
--- a/Source/Modules/ControllerModules/InputState.swift
+++ b/Source/Modules/ControllerModules/InputState.swift
@@ -57,10 +57,10 @@ import Cocoa
 ///   create a new user phrase.
 /// - Choosing Candidate: The candidate window is open to let the user to choose
 ///   one among the candidates.
-class InputState: NSObject {
+class InputState {
   /// Represents that the input controller is deactivated.
   class Deactivated: InputState {
-    override var description: String {
+    var description: String {
       "<InputState.Deactivated>"
     }
   }
@@ -73,7 +73,7 @@ class InputState: NSObject {
       ""
     }
 
-    override var description: String {
+    var description: String {
       "<InputState.Empty>"
     }
   }
@@ -86,7 +86,7 @@ class InputState: NSObject {
       ""
     }
 
-    override var description: String {
+    var description: String {
       "<InputState.EmptyIgnoringPreviousState>"
     }
   }
@@ -102,7 +102,7 @@ class InputState: NSObject {
       self.poppedText = poppedText
     }
 
-    override var description: String {
+    var description: String {
       "<InputState.Committing poppedText:\(poppedText)>"
     }
   }
@@ -119,7 +119,7 @@ class InputState: NSObject {
       self.cursorIndex = cursorIndex
     }
 
-    override var description: String {
+    var description: String {
       "<InputState.NotEmpty, composingBuffer:\(composingBuffer), cursorIndex:\(cursorIndex)>"
     }
   }
@@ -398,7 +398,7 @@ class InputState: NSObject {
       super.init()
     }
 
-    override var description: String {
+    var description: String {
       "<InputState.AssociatedPhrases, candidates:\(candidates), useVerticalMode:\(useVerticalMode)>"
     }
   }
@@ -421,20 +421,18 @@ class InputState: NSObject {
   }
 }
 
-class SymbolNode: NSObject {
+class SymbolNode {
   var title: String
   var children: [SymbolNode]?
 
   init(_ title: String, _ children: [SymbolNode]? = nil) {
     self.title = title
     self.children = children
-    super.init()
   }
 
   init(_ title: String, symbols: String) {
     self.title = title
     children = Array(symbols).map { SymbolNode(String($0), nil) }
-    super.init()
   }
 
   static let catCommonSymbols = String(
diff --git a/Source/Modules/ControllerModules/KeyHandler_Core.swift b/Source/Modules/ControllerModules/KeyHandler_Core.swift
index 7c7b0ff6..74883d32 100644
--- a/Source/Modules/ControllerModules/KeyHandler_Core.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_Core.swift
@@ -34,7 +34,7 @@ public enum InputMode: String {
 
 // MARK: - Delegate.
 
-protocol KeyHandlerDelegate: NSObjectProtocol {
+protocol KeyHandlerDelegate {
   func ctlCandidate(for _: KeyHandler) -> Any
   func keyHandler(
     _: KeyHandler, didSelectCandidateAt index: Int,
@@ -46,7 +46,7 @@ protocol KeyHandlerDelegate: NSObjectProtocol {
 
 // MARK: - Kernel.
 
-class KeyHandler: NSObject {
+class KeyHandler {
   let kEpsilon: Double = 0.000001
   var _composer: Tekkon.Composer = .init()
   var _inputMode: String = ""
@@ -55,7 +55,7 @@ class KeyHandler: NSObject {
   var _builder: Megrez.BlockReadingBuilder
   var _walkedNodes: [Megrez.NodeAnchor] = []
 
-  weak var delegate: KeyHandlerDelegate?
+  var delegate: KeyHandlerDelegate?
 
   var inputMode: InputMode {
     get {
@@ -71,9 +71,8 @@ class KeyHandler: NSObject {
     set { setInputMode(newValue.rawValue) }
   }
 
-  override init() {
+  public init() {
     _builder = Megrez.BlockReadingBuilder(lm: _languageModel)
-    super.init()
     ensureParser()
     setInputMode(ctlInputMethod.currentInputMode)
   }
diff --git a/Source/Modules/ControllerModules/vChewingKanjiConverter.swift b/Source/Modules/ControllerModules/vChewingKanjiConverter.swift
index c87692a3..bf95a42e 100644
--- a/Source/Modules/ControllerModules/vChewingKanjiConverter.swift
+++ b/Source/Modules/ControllerModules/vChewingKanjiConverter.swift
@@ -30,7 +30,7 @@ extension String {
   }
 }
 
-class vChewingKanjiConverter: NSObject {
+class vChewingKanjiConverter {
   class func cnvTradToKangXi(_ strObj: String) -> String {
     var strObj = strObj
     strObj.selfReplace("偽", "僞")
diff --git a/Source/Modules/FileHandlers/FSEventStreamHelper.swift b/Source/Modules/FileHandlers/FSEventStreamHelper.swift
index 69e5eff5..fe27953d 100644
--- a/Source/Modules/FileHandlers/FSEventStreamHelper.swift
+++ b/Source/Modules/FileHandlers/FSEventStreamHelper.swift
@@ -30,7 +30,7 @@ public protocol FSEventStreamHelperDelegate: AnyObject {
   func helper(_ helper: FSEventStreamHelper, didReceive events: [FSEventStreamHelper.Event])
 }
 
-public class FSEventStreamHelper: NSObject {
+public class FSEventStreamHelper {
   public struct Event {
     var path: String
     var flags: FSEventStreamEventFlags
diff --git a/Source/Modules/IMEModules/IME.swift b/Source/Modules/IMEModules/IME.swift
index df50d1b3..146316ec 100644
--- a/Source/Modules/IMEModules/IME.swift
+++ b/Source/Modules/IMEModules/IME.swift
@@ -28,7 +28,7 @@ import Cocoa
 // The namespace of this input method.
 public enum vChewing {}
 
-public class IME: NSObject {
+public class IME {
   static let arrSupportedLocales = ["en", "zh-Hant", "zh-Hans", "ja"]
   static let dlgOpenPath = NSOpenPanel()
 
diff --git a/Source/Modules/IMEModules/mgrPrefs.swift b/Source/Modules/IMEModules/mgrPrefs.swift
index 0bee5acc..0419b3b1 100644
--- a/Source/Modules/IMEModules/mgrPrefs.swift
+++ b/Source/Modules/IMEModules/mgrPrefs.swift
@@ -215,7 +215,7 @@ struct ComposingBufferSize {
 
 // MARK: -
 
-public class mgrPrefs: NSObject {
+public class mgrPrefs {
   static var allKeys: [String] {
     [
       UserDef.kIsDebugModeEnabled,
diff --git a/Source/Modules/LangModelRelated/mgrLangModel.swift b/Source/Modules/LangModelRelated/mgrLangModel.swift
index b72c0441..09ce44a4 100644
--- a/Source/Modules/LangModelRelated/mgrLangModel.swift
+++ b/Source/Modules/LangModelRelated/mgrLangModel.swift
@@ -36,7 +36,7 @@ private var gLangModelCHT = vChewing.LMInstantiator()
 private var gUserOverrideModelCHS = vChewing.LMUserOverride()
 private var gUserOverrideModelCHT = vChewing.LMUserOverride()
 
-class mgrLangModel: NSObject {
+class mgrLangModel {
   /// 寫幾個回傳函數、供其餘控制模組來讀取那些被設為 fileprivate 的器外變數。
   public static var lmCHS: vChewing.LMInstantiator { gLangModelCHS }
   public static var lmCHT: vChewing.LMInstantiator { gLangModelCHT }