【UE4 C++ 基礎知識】<3> 基本數據類型、字符串處理及轉換

基本數據類型

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TCHAR

• TCHAR就是UE4通過對char和wchar_t的封裝

  • char ANSI編碼
  • wchar_t 寬字符的Unicode編碼

• 使用 TEXT() 宏包裹作為字面值

  TCHAR* TCharString = TEXT("Hello, World!");
  
  	// 引擎字符串(TCHAR*) -> ANSI字符串(char*)
  	char* CharString = TCHAR_TO_ANSI(TCharString);
  
  	// 引擎字符串(TCHAR*) -> std::string
  	std::string str = TCHAR_TO_UTF8(TCharString);
  
  	// 引擎字符串(TCHAR*) -> wchar_t*
  	wchar_t* WCharString = TCHAR_TO_WCHAR(TCharString);
  
  	// ANSI字符串(char*) -> 引擎字符串(TCHAR*)
  	TCHAR* TCharString1 = ANSI_TO_TCHAR(CharString);
  
  	// wchar_t* -> 引擎字符串(TCHAR*)
  	TCHAR* TCharString2 = UTF8_TO_TCHAR(WCharString);
  	TCHAR* TCharString3 = WCHAR_TO_TCHAR(WCharString);
  

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FNames

常用作標識符等不變的字符串（如：資源路徑/資源文件類型/骨骼名稱/表格行名等）

• 比較字符串操作非常快
• 即使多個相同的字符串，也只在內存存儲一份副本，避免了冗余的內存分配操作
• 不區分大小寫

使用

• 初始化

  FName TestHUDName = FName(TEXT("ThisIsMyTestFName"));
  

• 比較

  CompareFloat = TestFName.Compare(OtherFName);
  

• 搜索

  if( FName(TEXT("pelvis"), FNAME_Find) != NAME_None ){}
  

• FString <-> FName

  TestHUDName = FName(*TestHUDString);
  TestHUDString = TestHUDName.ToString();
  

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FText

FText 是一種靜態字符串，在UE4中可以負責處理文本本地化、UI 文本顯示等

• 支持文本本地化
• 提高文本渲染的性能
• 較快的copy操作

使用

• FString <-> FText

  TestHUDText = FText::FromString(TestHUDString);
  TestHUDString = TestHUDText.ToString();
  

• FName -> FText

  TestHUDText = FText::FromName(TestHUDName);
  

• 比較
  

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FString

初始化

FString str1("Hello!");

FString str2 = TEXT("Hello World!");

FString str3 = FString::Printf(TEXT("I am %d years old"), 18);

比較

if(MyFString.Equals(OtherFString, ESearchCase::CaseSensitive)){...} // 大小寫敏感
if(MyFString.Equals(OtherFString, ESearchCase::IgnoreCase)){...}
if(MyFString == OtherFString){...}

拼接

FString str4 = TEXT("Hello World!");
str4 += FString("UE4");

float value = 1.0f;
FString str5 = FString::Printf(TEXT("Current Value: %f"),value);

分割

FString str6 = TEXT("Blueprint, C++, Material");
TArray<FString> strList;
str6.ParseIntoArray(strList, TEXT(","), true);

FString 與其他類型字符串轉換

• FString <-> int32/float

  // FString -> int32/float
  FString TheString = "233";
  int32 MyShinyNewInt = FCString::Atoi(*TheString);
  
  FString TheString = "233.3";
  float MyStringtoFloat = FCString::Atof(*TheString);
  
  // int32/float -> FString
  FString NewString = FString::FromInt(233);
  FString NewString = FString::SanitizeFloat(233.3f);
  

• FString <-> TCHAR* 自動隱式轉換

  const FString MyFString;
  const TCHAR *TCharString = *MyFString;
  
  const FString MyFString=TCharString;
  

• FString → char *

  // 1
  char *plainText= TCHAR_TO_ANSI(*str);
  
  // 2
  FString str
  string t = TCHAR_TO_UTF8(*str);
  char * returnvalue = (char *)malloc(sizeof(char) * (t.length() + 1));
  strncpy_s(returnvalue, t.length() , t.c_str(), t.length());  
  
  

• FString <-> std::string

  // FString -> std::string
  FString UE4Str = "Flowers";
  std::string MyStdString(TCHAR_TO_UTF8(*UE4Str));
  
  // std::string -> FString
  std::string TestString = "Happy"; 
  FString HappyString(TestString.c_str());
  

• FString <-> TArray

  // FString -> TArray<uint8>
  FString JsonStr;  
  TArray<uint8> content;  
  content.SetNum(JsonStr.Len());  
  memcpy(content.GetData(), TCHAR_TO_ANSI(*JsonStr), JsonStr.Len()); 
  
  //TArray<uint8> ****-> FString 
  TArray<uint8> content;  
  const std::string cstr(reinterpret_cast<const char*>(content.GetData()), content.Num());  
  FString frameAsFString = cstr.c_str();  
  UE_LOG(VRSLog, Warning, TEXT("%s"), *frameAsFString);   
  

• FArrayReaderPtr -> FString

  uint8 data[512];  
  FMemory::Memzero(data, 512);  
  FMemory::Memcpy(data, ArrayReaderPtr->GetData(), ArrayReaderPtr->Num());  
  FString str = ((const char*)data);  
  

• 數值 -> std::to_string

  std::string to_string( long value );
  std::string to_string( long long value );
  std::string to_string( unsigned value );
  std::string to_string( unsigned long value );
  std::string to_string( unsigned long long value );
  std::string to_string( float value );
  std::string to_string( double value );
  std::string to_string( long double value );
  

• std::string <-> std::wstring

  • WideCharToMultiByte

  
  // std::wstring -> std::string
  std::string WStringToString(const std::wstring wstr)
  {
  	std::string str;
  	int len = WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), wstr.size(), NULL, 0, NULL,NULL);
  	char*buffer = new char[len + 1];
  	WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), wstr.size(), buffer, len, NULL, NULL);
  	buffer[len] = '\0';
  	str.append(buffer);
  	delete[]buffer;
  	return str;
  }
  
  //  std::string -> std::wstring
  std::string str_path=TCHAR_TO_UTF8(*AppPath);
  std::wstring wstr_path;
  wstr_path.assign(str_path.begin(), str_path.end());
  

其他

• 中文亂碼

• UE4 Source Header References

  CString.h
  UnrealString.h
  NameTypes.h
  StringConv.h (TCHAR_TO_ANSI etc)
  

• CString.h可以查到更多，如

  toi64 (string to int64)
  Atod    (string to double precision float)
  

• 更多關於FString的操作可以到UnrealString.h找到.

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參考

• 虛幻引擎4 官方文檔 | 字符串
• UE4 C++基礎教程 - 字符串和本地化