windows 在cpp中将字符串转换为_T
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convert string to _T in cpp
提问by yogi
I want to convert stringor char*to the _Tbut not able to do.
我想转换string或转换char*为_T但无法做到。
if i write
如果我写
_tcscpy(cmdline,_T ("hello world"));
it works perfectly, but if i write
它工作得很好，但如果我写
char* msg="hello world";
_tcscpy(cmdline,_T (msg));
it shows an error like: error C2065: 'Lmsg' : undeclared identifier
它显示如下错误： error C2065: 'Lmsg' : undeclared identifier
Please give me a solution.
请给我一个解决方案。
Thanx in advance.
提前谢谢。
回答by Nawaz
_Tis a macro, defined as (if UNICODEis defined):
_T是一个宏，定义为（如果UNICODE已定义）：
#define _T(a) L ## a
which can work only with string-literals. So when you write _T("hi")it becomes L"hi"which is valid, as expected. But when you write _T(msg)it becomes Lmsgwhich is an undefined identifier, and you didn't intend that.
它只能与字符串文字一起使用。因此，当您编写_T("hi")它时L"hi"，它就像预期的那样有效。但是当您编写_T(msg)它时Lmsg，它变成了一个未定义的标识符，而您并不打算这样做。
All you need is this function mbstowcsas:
您所需要的只是这个功能mbstowcs：
const char* msg="hello world"; //use const char*, instead of char*
wchar_t *wmsg = new wchar_t[strlen(msg)+1]; //memory allocation
mbstowcs(wmsg, msg, strlen(msg)+1);
//then use wmsg instead of msg
_tcscpy(cmdline, wmsg);
//memory deallocation - must do to avoid memory leak!
delete []wmsg;
回答by NPE
_Tonly works with string literals. All it does is turn the literal into an L""string if the code's being compiled with Unicode support, or leave it alone otherwise.
_T仅适用于字符串文字。L""如果代码是在支持 Unicode 的情况下编译的，那么它所做的就是将文字转换为字符串，否则将其置之不理。
Take a look at http://msdn.microsoft.com/en-us/library/dybsewaf(v=vs.80).aspx
看看http://msdn.microsoft.com/en-us/library/dybsewaf(v=vs.80).aspx
回答by Ajay
回答by Jon
_Tis a macro that makes string literals into wide-char string literals by prepending an Lbefore the literal in UNICODEbuilds.
_T是一个宏，它通过L在UNICODEbuilds 中的文字前添加 an 来将字符串文字转换为宽字符字符串文字。
In other words, when you write _T("Hello")it is as if you had written "Hello"on an ANSI build or L"Hello"on a UNICODE build. The type of the resulting expression is char*or wchar_t*respectively.
换句话说，当您编写_T("Hello")它时，就好像您是"Hello"在 ANSI 版本或L"Hello"UNICODE 版本上编写的。结果表达式的类型分别为char*或wchar_t*。
_Tcan notconvert a string variable(std::stringor char*) to a wchar_t*-- for this, you have to use a function like mbstowcsor MultiByteToWideChar.
_T不能将字符串变量( std::stringor char*)转换为 a wchar_t*-- 为此，您必须使用类似mbstowcsor的函数MultiByteToWideChar。
Suggestion:It will be much easier for you (and in no way worse) to always make a UNICODE build and forget about _T, TCHARand all other T-derivatives. Just use wide-character strings everywhere.
建议：这将是您更容易（并且绝不更糟）总是做一个UNICODE构建和忘记_T，TCHAR和所有其他T-衍生物。只需在任何地方使用宽字符串。
回答by unkulunkulu
_Tis not an actual type. It's a macro that prepends string literalswith Lso that they would be wchar_t*s instead of char*. If you need to convert a char*string to wchar_t*one at runtime, you need mbtowcsfor example.
_T不是实际类型。这是一个宏，预先考虑字符串文字与L这样他们就可以wchar_t*！而非char*。如果您需要在运行时将char*字符串转换为一个字符串，例如wchar_t*您需要mbtowcs。
回答by Gearoid Murphy
The _T modifier is just a declaration to tell the compiler that the string literal must be interpreted as a utf-16 encoding. The reason it doesn't work on the variable is because the contents of that variable have already been declared as ascii.
_T 修饰符只是一个声明，告诉编译器必须将字符串文字解释为 utf-16 编码。它对变量不起作用的原因是因为该变量的内容已经声明为 ascii。
As already mentioned the mbstowcsfunction is what you need to perform the conversion of a char data into utf-16 (wide char) data.
如前所述，mbstowcs函数是将 char 数据转换为 utf-16（宽字符）数据所需的函数。
