Convert std::string to FString

Development Programming & Scripting C++
1

Is there a straightforward way to convert a std::string into an FString?

2

You should be able to do it with something like:

UTF8_TO_TCHAR(str.c_str())

There are three other important conversion functions available in StringConv.h

Be aware that this conversion is ā€œshort livedā€ and it is suggested that they only be used as function parameters.

1 Like
4

To add more to the discussion:

I had no trouble just doing this:



#include <string>

//....

some function
{
  std::string TestString = "Happy"; 
  FString HappyString(TestString.c_str());
}

You might want to check out UnrealString.h to see exactly how this is occurring :slight_smile:

Rama

PS: Bob_Gneu I really like your quote in your signature :heart:

7 Likes
5

Thanks guys!

Rama, your solution worked perfectly and it was so simple :). Iā€™ll definitely take a look at UnrealString.h

6

I recently had to use TCHAR_TO_UTF8,

so I wanted to take a moment to thank Bob Gneu for mentioning StringConv.h

Thanks Bob Gneu!

:slight_smile:

Rama

7

How could it be done in reverse? Convert FString to std::string?

8

It can.

Check out **StringConv.h **it has a number of methods that swap back and forth between the types.

// Usage of these should be replaced with StringCasts.
#define TCHAR_TO_ANSI(str) (ANSICHAR*)StringCast<ANSICHAR>(static_cast<const TCHAR*>(str)).Get()
#define ANSI_TO_TCHAR(str) (TCHAR*)StringCast<TCHAR>(static_cast<const ANSICHAR*>(str)).Get()
#define TCHAR_TO_UTF8(str) (ANSICHAR*)FTCHARToUTF8((const TCHAR*)str).Get()
#define UTF8_TO_TCHAR(str) (TCHAR*)FUTF8ToTCHAR((const ANSICHAR*)str).Get()

9

Full Two Way Code

Bob is correct of course :slight_smile:

I just wrote up this code for you if you need exact code to work with!



FString UE4Str = "UE4 C++"; 

**//FString to std::string**
std::string cstr(TCHAR_TO_UTF8(*UE4Str));

**//std::string to FString**
ClientMessage(FString(cstr.c_str()));

Recall that operator* for FString gets you the inner data, which is TCHAR*

Enjoy!

Rama

PS: to run this code you need to #include <string>

3 Likes
10

char*

Hi Rama (and everybody)!

I must admit Iā€™ve been lurking in the forums for quite some time now, but I never dared to post. Now, however I have a matter that needs solving:

What if I need to convert to char* ? Iā€™m currently doing this, but it doesnā€™t strike me as nice code:


FString hlString = "Whatever";
std::string mlString(TCHAR_TO_UTF8(*hlString));
char* llString = &mlString[0];

Somehow the back of my brain tingles saying ā€œmemory managementā€ with the last line, but this is the best approximation of what I want based on multiple StackOverflow answers (except maybe the vector approach, but I do need a raw char*). Is there any way I could improve this? Also, is it okay to use TCHAR_TO_ANSI if I can guarantee only ANSI chars will be used? Is there any benefit in doing so?

As far as I can imagine, the inverse case is much safer, considering Iā€™ve already managed the char*, isnā€™t it?


char* llString = "Something";
std::string mlString(llString);
FString hlString(FString(mlString.c_str()));

P.S.: Thanks for EVERYTHING you post, itā€™s a source of inspiration and it is always helpful.

11

Hi there!

[FONT=Comic Sans MS]**Welcome to the forums! **

You should post more often, you are a very eloquent writer!

Youā€™re welcome!

:slight_smile:


Regarding your q:

This was the best answer I saw, for writable char * see the thread itself;
http://stackoverflow.com/questions/347949/how-to-convert-a-stdstring-to-const-char-or-char

for **readonly** char* you can use this:



```


FString UE4Str = "UE4 C++"; 

//FString to std::string
std::string Your_Cstr(TCHAR_TO_UTF8(*UE4Str)):

//char*
const char * ReadOnlyCharPtr = Your_Cstr.c_str();


```



Rama
12

Wow! Thanks for the kind words and for answering so quickly. Iā€™m posting the two resulting utility functions, in case anybody else can make use of them:


char* fstring2charp(FString highLevelString) {
	std::string midLevelString(TCHAR_TO_UTF8(*highLevelString));
	char* lowLevelString = new char[midLevelString.size()+1];
	std::copy(midLevelString.begin(), midLevelString.end(), lowLevelString);
	return lowLevelString;
}

FString charp2fstring(char* lowLevelString){
	std::string midLevelString(lowLevelString);
	FString highLevelString(FString(midLevelString.c_str()));
	return highLevelString;
}

Iā€™m aware they are more verbose than they would need to be, Iā€™ve left them like that for clarityā€™s sake. Also, Iā€™m not exactly sure what happens on the memory management level; for instance, can we call delete on the resulting pointer of a call to fstring2charp?

Donā€™t forget to #include <string>, <algorithm>

13

It seems that when ā€˜UE4Strā€™ contains Chinese characters,this approach does not work well.

14

All Unicode characters have a problem when coerced into ascii characters. Your best bet is likely the macros I mentioned earlier.

15

What you want to be using is std::wstring, not std::string.

16

Just curious. It is said that UE4 doesnā€™t support std. How could you use std here?

17

While itā€™s not recommended to mix Unrealā€™s string containers and std::string, thereā€™s nothing really stopping you from using the STL. Searching the engine source for ā€œstd::stringā€ does bring up a few results.

18

Thanks for your reply. I just met an issue when importing third party library with std:vector as input parameter and trying to wrap it. I had thought std is totally not allowed in UE4.

20

FString UE4Str = ā€œUE4 C++ 包含äø­ę–‡ā€;
//FString to std::string

std::string cstr(TCHAR_TO_UTF8(*UE4Str));

//std::string to FString éœ€č¦ä½æē”ØUTF8_TO_TCHAR åœØč½¬äø€ę¬”

ClientMessage(FString(UTF8_TO_TCHAR(cstr.c_str())));

2 Likes