diff --git a/Source/Modules/ControllerModules/InputState.swift b/Source/Modules/ControllerModules/InputState.swift
index e5735965..e76d3608 100644
--- a/Source/Modules/ControllerModules/InputState.swift
+++ b/Source/Modules/ControllerModules/InputState.swift
@@ -490,8 +490,8 @@ public enum InputState {
             return cursorIndexU8..<min(cursorIndexU8 + chosenCandidateString.count, composingBuffer.count - 1)
         }
       }()
-      let strSegmentedRear = composingBuffer.map { String($0) }[0..<u8Range.lowerBound].joined()
-      let strSegmentedFront = composingBuffer.map { String($0) }[u8Range.upperBound...].joined()
+      let strSegmentedRear = composingBuffer.charComponents[0..<u8Range.lowerBound].joined()
+      let strSegmentedFront = composingBuffer.charComponents[u8Range.upperBound...].joined()
       let newBufferConverted: String = NotEmpty(
         composingBuffer: strSegmentedRear + chosenCandidateString + strSegmentedFront, cursorIndex: 0
       ).composingBufferConverted
diff --git a/Source/Modules/ControllerModules/KeyHandler_Core.swift b/Source/Modules/ControllerModules/KeyHandler_Core.swift
index f6c62541..a6963c66 100644
--- a/Source/Modules/ControllerModules/KeyHandler_Core.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_Core.swift
@@ -184,7 +184,7 @@ public class KeyHandler {
           position += currentNode.keyArray.count
           continue
         }
-        let values = currentNode.currentPair.value.map { String($0) }
+        let values = currentNode.currentPair.value.charComponents
         for (subPosition, key) in currentNode.keyArray.enumerated() {
           guard values.count > subPosition else { break }  // 防呆，應該沒有發生的可能性
           let thePair = Megrez.Compositor.Candidate(
diff --git a/Source/Modules/ControllerModules/KeyHandler_States.swift b/Source/Modules/ControllerModules/KeyHandler_States.swift
index f39757bd..0c1166dc 100644
--- a/Source/Modules/ControllerModules/KeyHandler_States.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_States.swift
@@ -30,7 +30,7 @@ extension KeyHandler {
     /// 這樣就可以免除不必要的類型轉換。
     for theNode in compositor.walkedNodes {
       let strNodeValue = theNode.value
-      let arrSplit: [String] = Array(strNodeValue).map { String($0) }
+      let arrSplit: [String] = Array(strNodeValue).charComponents
       let codepointCount = arrSplit.count
       /// 藉下述步驟重新將「可見游標位置」對齊至「組字器內的游標所在的讀音位置」。
       /// 每個節錨（NodeAnchor）都有自身的幅位長度（spanningLength），可以用來
diff --git a/Source/Modules/LangModelRelated/SubLMs/lmPlainBopomofo.swift b/Source/Modules/LangModelRelated/SubLMs/lmPlainBopomofo.swift
index 6a689e5c..e0114bf7 100644
--- a/Source/Modules/LangModelRelated/SubLMs/lmPlainBopomofo.swift
+++ b/Source/Modules/LangModelRelated/SubLMs/lmPlainBopomofo.swift
@@ -58,7 +58,7 @@ extension vChewing {
     public func valuesFor(key: String) -> [String] {
       var pairs: [String] = []
       if let arrRangeRecords: String = rangeMap[key] {
-        pairs.append(contentsOf: arrRangeRecords.map { String($0) })
+        pairs.append(contentsOf: arrRangeRecords.charComponents)
       }
       var set = Set<String>()
       return pairs.filter { set.insert($0).inserted }
diff --git a/vChewingTests/KeyHandlerTestsNormalCHS.swift b/vChewingTests/KeyHandlerTestsNormalCHS.swift
index 9600ee12..832c8bd3 100644
--- a/vChewingTests/KeyHandlerTestsNormalCHS.swift
+++ b/vChewingTests/KeyHandlerTestsNormalCHS.swift
@@ -467,9 +467,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testInvalidBpmf() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("eul4").map {
-      String($0)
-    }
+    let keys = Array("eul4").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -482,9 +480,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testInputting() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("18 m,45j/ fu. g0 xup6xu;6").map {
-      String($0)
-    }
+    let keys = Array("18 m,45j/ fu. g0 xup6xu;6").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -500,9 +496,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testInputtingNihao() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -518,9 +512,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testInputtingTianKong() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("wu0 dj/ ").map {
-      String($0)
-    }
+    let keys = Array("wu0 dj/ ").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -536,9 +528,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testCommittingNihao() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -580,9 +570,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testDelete() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -662,9 +650,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testBackspaceToDeleteReading() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su").map {
-      String($0)
-    }
+    let keys = Array("su").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -696,9 +682,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testBackspaceAtBegin() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -739,9 +723,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testBackspaceToDeleteReadingWithText() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl").map {
-      String($0)
-    }
+    let keys = Array("su3cl").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -777,9 +759,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testBackspace() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -818,9 +798,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testCursorWithReading() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl").map {
-      String($0)
-    }
+    let keys = Array("su3cl").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -855,9 +833,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testCursor() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -948,9 +924,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testCandidateWithDown() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -985,9 +959,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.chooseCandidateUsingSpace
     mgrPrefs.chooseCandidateUsingSpace = true
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1023,9 +995,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.chooseCandidateUsingSpace
     mgrPrefs.chooseCandidateUsingSpace = false
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: InputState.Empty()) { newState in
@@ -1079,9 +1049,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.chooseCandidateUsingSpace
     mgrPrefs.chooseCandidateUsingSpace = false
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1117,9 +1085,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testHomeAndEnd() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1191,9 +1157,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testHomeAndEndWithReading() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl").map {
-      String($0)
-    }
+    let keys = Array("su3cl").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1245,9 +1209,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testMarkingLeftAtBegin() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1279,9 +1241,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testMarkingRightAtEnd() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1304,9 +1264,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testMarkingLeft() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1371,9 +1329,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testMarkingRight() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1455,9 +1411,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
 
   func testCancelMarking() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl3").map {
-      String($0)
-    }
+    let keys = Array("su3cl3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1503,9 +1457,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.escToCleanInputBuffer
     mgrPrefs.escToCleanInputBuffer = false
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su").map {
-      String($0)
-    }
+    let keys = Array("su").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1535,9 +1487,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.escToCleanInputBuffer
     mgrPrefs.escToCleanInputBuffer = false
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl").map {
-      String($0)
-    }
+    let keys = Array("su3cl").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
@@ -1571,9 +1521,7 @@ class KeyHandlerTestsNormalCHS: XCTestCase {
     let enabled = mgrPrefs.escToCleanInputBuffer
     mgrPrefs.escToCleanInputBuffer = true
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3cl").map {
-      String($0)
-    }
+    let keys = Array("su3cl").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalTyping: false)
       _ = handler.handle(input: input, state: state) { newState in
diff --git a/vChewingTests/KeyHandlerTestsSCPCCHT.swift b/vChewingTests/KeyHandlerTestsSCPCCHT.swift
index 4c1fd5f3..a3daf0e4 100644
--- a/vChewingTests/KeyHandlerTestsSCPCCHT.swift
+++ b/vChewingTests/KeyHandlerTestsSCPCCHT.swift
@@ -190,9 +190,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
 
   func testInputNi() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su").map {
-      String($0)
-    }
+    let keys = Array("su").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in
@@ -209,9 +207,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
 
   func testInputNi3() {
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in
@@ -230,9 +226,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
   func testCancelCandidateUsingDelete() {
     mgrPrefs.useSCPCTypingMode = true
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in
@@ -257,9 +251,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
   func testCancelCandidateUsingEsc() {
     mgrPrefs.useSCPCTypingMode = true
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("su3").map {
-      String($0)
-    }
+    let keys = Array("su3").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in
@@ -285,9 +277,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
     mgrPrefs.useSCPCTypingMode = true
     handler.forceOpenStringInsteadForAssociatePhrases("二 百五")
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("-41").map {
-      String($0)
-    }
+    let keys = Array("-41").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in
@@ -308,9 +298,7 @@ class KeyHandlerTestsSCPCCHT: XCTestCase {
     let enabled = mgrPrefs.associatedPhrasesEnabled
     mgrPrefs.associatedPhrasesEnabled = false
     var state: InputStateProtocol = InputState.Empty()
-    let keys = Array("aul ").map {
-      String($0)
-    }
+    let keys = Array("aul ").charComponents
     for key in keys {
       let input = InputSignal(inputText: key, keyCode: 0, charCode: charCode(key), flags: [])
       _ = handler.handle(input: input, state: state) { newState in