diff --git a/Source/WindowControllers/ctlPrefWindow.swift b/Source/WindowControllers/ctlPrefWindow.swift
index b2b11896..521b5c1d 100644
--- a/Source/WindowControllers/ctlPrefWindow.swift
+++ b/Source/WindowControllers/ctlPrefWindow.swift
@@ -90,52 +90,43 @@ extension RangeReplaceableCollection where Element: Hashable {
         basisKeyboardLayoutButton.menu?.addItem(menuItem_vChewingDachen)
 
         let basisKeyboardLayoutID = Preferences.basisKeyboardLayout
-        
+
         for source in list {
-
-            func getString(_ key: CFString) -> String? {
-                if let ptr = TISGetInputSourceProperty(source, key) {
-                    return String(Unmanaged<CFString>.fromOpaque(ptr).takeUnretainedValue())
-                }
-                return nil
-            }
-
-            func getBool(_ key: CFString) -> Bool? {
-                if let ptr = TISGetInputSourceProperty(source, key) {
-                    return Unmanaged<CFBoolean>.fromOpaque(ptr).takeUnretainedValue() == kCFBooleanTrue
-                }
-                return nil
-            }
-
-            if let category = getString(kTISPropertyInputSourceCategory) {
-                if category != String(kTISCategoryKeyboardInputSource) {
+            if let categoryPtr = TISGetInputSourceProperty(source, kTISPropertyInputSourceCategory) {
+                let category = Unmanaged<CFString>.fromOpaque(categoryPtr).takeUnretainedValue()
+                if category != kTISCategoryKeyboardInputSource {
                     continue
                 }
             } else {
                 continue
             }
 
-            if let asciiCapable = getBool(kTISPropertyInputSourceIsASCIICapable) {
-                if !asciiCapable {
+            if let asciiCapablePtr = TISGetInputSourceProperty(source, kTISPropertyInputSourceIsASCIICapable) {
+                let asciiCapable = Unmanaged<CFBoolean>.fromOpaque(asciiCapablePtr).takeUnretainedValue()
+                if asciiCapable != kCFBooleanTrue {
                     continue
                 }
             } else {
                 continue
             }
 
-            if let sourceType = getString(kTISPropertyInputSourceType) {
-                if sourceType != String(kTISTypeKeyboardLayout) {
+            if let sourceTypePtr = TISGetInputSourceProperty(source, kTISPropertyInputSourceType) {
+                let sourceType = Unmanaged<CFString>.fromOpaque(sourceTypePtr).takeUnretainedValue()
+                if sourceType != kTISTypeKeyboardLayout {
                     continue
                 }
             } else {
                 continue
             }
 
-            guard let sourceID = getString(kTISPropertyInputSourceID),
-                  let localizedName = getString(kTISPropertyLocalizedName) else {
+            guard let sourceIDPtr = TISGetInputSourceProperty(source, kTISPropertyInputSourceID),
+                  let localizedNamePtr = TISGetInputSourceProperty(source, kTISPropertyLocalizedName) else {
                 continue
             }
 
+            let sourceID = String(Unmanaged<CFString>.fromOpaque(sourceIDPtr).takeUnretainedValue())
+            let localizedName = String(Unmanaged<CFString>.fromOpaque(localizedNamePtr).takeUnretainedValue())
+
             let menuItem = NSMenuItem()
             menuItem.title = localizedName
             menuItem.representedObject = sourceID