UE4 essays: fstring, fname and ftext

FString、FName And FText

    UE4 There are three classes that handle strings in , To meet different development needs ：FString、FName and FText, Between the three difference by ：

① FName

Focus on expressing name , Case insensitive , Non modifiable , The resource names in the engine are FName type , Reusing strings through a lightweight system ,FName When creating, a... Will be created according to the content Hash value , And the same content will only be stored once . adopt Hash Value in progress FName Is faster to find and access , In comparison , There is no need to compare the string contents , Direct comparison Hash Value to distinguish between different FName character string .

The other two strings go to FName Transformation （ Special note ,FText Cannot convert directly to FName, Can be converted to FString, Re convert to FName）：

FString str = TEXT("Hello world~");
FText txt = LOCTEXT("keyName", "theValue");
FText txtNS = NSLOCTEXT("TextNameSpace", "keyName", "theValue");

// FString  turn  FName： unreliable , Missing case information 
FName name1 = FName(*str);

FString strFromTxt = txt.ToString();
// FText  Turn first  FString, Re turn  FName： unreliable , Missing case information , The loss of localization information may lead to the potential risk of language conversion 
FName name2 = FName(*strFromTxt);

② FString

Nearest std::string, The point is String operation , It provides a large number of operation interfaces for strings , Is the only modifiable string type among the three , And that's why ,FString It is more expensive than the other two strings , Lower performance .

The other two strings go to FString Transformation ：

FName name = TEXT("I am Frank~");
FText txt = LOCTEXT("keyName", "theValue");
FText txtNS = NSLOCTEXT("TextNameSpace", "keyName", "theValue");

// FName  turn  FString： reliable 
FString str1 = name.ToString();
// FText  turn  FString： unreliable , The loss of localization information may lead to the potential risk of language conversion 
FString str2 = txt.ToString();

③ FText

The point is Display and localization , Display information that can be directly seen by understandable players , Localization is multilingual processing , Non modifiable . Compared with the other two types ,FText Will be more bloated , But it provides excellent localization capabilities .

The other two strings go to FText Transformation ：

FString str = TEXT("Hello world~");
FName name = TEXT("I am Frank~");

// FString  turn  FText： reliable 
FText txt1 = FText::FromString(str);
// FName  turn  FText： reliable 
FText txt2 = FText::FromName(name);

It should be noted that , establish FText The control needs to be named and defined Namespace , And open it in the editor Localize control panel features （Localization Dashboard）：

I.   Declare a text space macro in the current source file , Create... Within the scope of the macro declaration FText Namespace parameters are not required , It is important to note that the declaration must be undeclared at the end of the source file ：

// Source.cpp
//  Declare text space macros 
#define LOCTEXT_NAMESPACE "MyTextNameSpace"

//  Macro declaration scope creation FText
FText txt = LOCTEXT("keyName", "theValue");

//  The declaration must be cancelled in the appropriate place 
#undef LOCTEXT_NAMESPACE

    II. Define the namespace in the editor , Can be used directly in code ：

//  Use the defined namespace 
FText txtNS = NSLOCTEXT("TextNameSpace", "keyName", "theValue");