那些遇到过的问题

C++的String.Format

Dou*_*ugN 27 c++ string.format printf localization

寻找像.NET的String.Format这样的函数的C++实现.显然有printf和它的品种,但我正在寻找一些位置如下的东西:

String.Format("你好{0}.你已经{1}岁了.感觉{1}怎么样？",姓名,年龄);

这是必要的,因为我们将尝试更轻松地本地化我们的应用程序,并将翻译器{0}和{1}放在句子中的任何位置比给他们%s,%d,%要容易得多d必须按其顺序排列.

我认为搜索和替换变量输入(va_start,va_end等)是我最终要构建的,但如果已经有一个可靠的解决方案,那将是首选.

谢谢 :)

sho*_*osh 15

QT的QString允许你这样做:

QString("Hi there %1. You are %2 years old. How does it feel \
         to be %2?").arg(name).arg(age)
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  • QtCore支持使用QObject :: tr进行国际化.它返回带有%1,%2等占位符的QString.它还允许一个特殊的%n,它允许单词正确复数. (2认同)

Log*_*ldo 10

信不信由你,printf和朋友支持位置论证.

 #include <stdio.h>

 int main() {
   char *name = "Logan";
   int age = 25;
   printf("Hi there %1$s, you are %2$d years old. How does it feel to be %2$d?\n", name, age);
  return 0;
 }
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  • 关于标准的奇妙之处在于有很多可供选择.例如http://www.opengroup.org/onlinepubs/000095399/functions/printf.html它是XSI标准. (6认同)
  • 如果您不想打印它,请使用sprintf/snprintf. (2认同)

Chr*_*rdt 7

您可以查看FastFormat -library.

Dou*_*ugN 3

上面有很多好的建议，在大多数情况下都适用。就我而言，我最终希望从资源加载字符串，并尽可能使字符串资源接近 .NET String.Format，因此我推出了自己的资源。在查看了上面的一些实现以获取想法之后，最终的实现非常简短且简单。

有一个 String 类，在我的例子中，它派生自 Microsoft 的 CString，但它可以派生自任何字符串类。还有一个 StringArg 类——它的作用是获取任何参数类型并将其转换为字符串（即它模仿 .NET 中的 ToString）。如果需要对新对象进行 ToString 处理，只需添加另一个构造函数即可。构造函数允许使用 printf 样式的格式说明符进行非默认格式设置。

然后，String 类接受源字符串的字符串表 ID、许多 StringArg 参数，最后是一个可选的 HINSTANCE（我使用很多 DLL，其中任何一个都可以托管字符串表，因此这允许我将其传递进去，或者默认使用特定于 DLL 的 HINSTANCE）。

用法示例：

dlg.m_prompt = String(1417); //"Welcome to Stackoverflow!"
MessageBox(String(1532, m_username)); //"Hi {0}"
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事实上，它只需要一个字符串 ID 作为输入，但添加输入字符串而不是字符串 ID 会很简单：

CString s = String.Format("Hi {0}, you are {1} years old in Hexidecimal", m_userName, StringArg(m_age, "%0X"));
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现在对于 StringArg 类，它对变量执行与 ToString 相同的操作：

class StringArg
{
StringArg(); //not implemented
        StringArg(const StringArg&); //not implemented
        StringArg& operator=(const StringArg&); //not implemented

    public:
        StringArg(LPCWSTR val);
    StringArg(const CString& val);
    StringArg(int val, LPCWSTR formatSpec = NULL);
    StringArg(size_t val, LPCWSTR formatSpec = NULL);
    StringArg(WORD val, LPCWSTR formatSpec = NULL);
    StringArg(DWORD val, LPCWSTR formatSpec = NULL);
    StringArg(__int64 val, LPCWSTR formatSpec = NULL);
    StringArg(double val, LPCWSTR formatSpec = NULL);
    CString ToString() const;
private:
    CString m_strVal;
};

extern HINSTANCE GetModuleHInst(); //every DLL implements this for getting it's own HINSTANCE -- scenarios with a single resource DLL wouldn't need this
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对于 String 类，有一堆成员函数和构造函数，最多需要 10 个参数。这些最终调用 CentralFormat 来完成真正的工作。

class String : public CString
{
public:
    String() { }
    String(WORD stringTableID, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, hInst); }
    String(WORD stringTableID, const StringArg& arg1, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, arg5, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, arg5, arg6, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, arg5, arg6, arg7, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, hInst); }
    String(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, const StringArg& arg9, HINSTANCE hInst = GetModuleHInst()) { Format(stringTableID, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, hInst); }


    CString& Format(WORD stringTableID, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, HINSTANCE hInst = GetModuleHInst());
    CString& Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, const StringArg& arg9, HINSTANCE hInst = GetModuleHInst());
private:
    void CentralFormat(WORD stringTableID, std::vector<const StringArg*>& args, HINSTANCE hInst);
};
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最后是实现（希望在 StackOverflow 上发布这么多内容是可以的，尽管其中大部分内容非常简单）：

StringArg::StringArg(LPCWSTR val)
{
    m_strVal = val;
}

StringArg::StringArg(const CString& val)
{
    m_strVal = (LPCWSTR)val;
}

StringArg::StringArg(int val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%d"; //GLOK
    m_strVal.Format(formatSpec, val);
}

StringArg::StringArg(size_t val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%u"; //GLOK
    m_strVal.Format(formatSpec, val);
}

StringArg::StringArg(WORD val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%u"; //GLOK
    m_strVal.Format(formatSpec, val);
}

StringArg::StringArg(DWORD val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%u"; //GLOK
    m_strVal.Format(formatSpec, val);
}

StringArg::StringArg(__int64 val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%I64d"; //GLOK
    m_strVal.Format(formatSpec, val);
}

StringArg::StringArg(double val, LPCWSTR formatSpec)
{
    if(NULL == formatSpec)
        formatSpec = L"%f"; //GLOK
    m_strVal.Format(formatSpec, val);
}

CString StringArg::ToString() const
{ 
    return m_strVal; 
}


void String::CentralFormat(WORD stringTableID, std::vector<const StringArg*>& args, HINSTANCE hInst)
{
    size_t argsCount = args.size();
    _ASSERT(argsCount < 10); //code below assumes a single character position indicator

    CString tmp;
    HINSTANCE hOld = AfxGetResourceHandle();
    AfxSetResourceHandle(hInst);
    BOOL b = tmp.LoadString(stringTableID);
    AfxSetResourceHandle(hOld);
    if(FALSE == b)
    {
#ifdef _DEBUG

        //missing string resource, or more likely a bad stringID was used -- tell someone!!
    CString s;
        s.Format(L"StringID %d could not be found!  %s", stringTableID, hInst == ghCommonHInst ? L"CommonHInst was passed in" : L"CommonHInst was NOT passed in"); //GLOK
        ::MessageBeep(MB_ICONHAND);
        ::MessageBeep(MB_ICONEXCLAMATION);
        ::MessageBeep(MB_ICONHAND);
        _ASSERT(0);
        ::MessageBox(NULL, s, L"DEBUG Error - Inform Development", MB_ICONSTOP | MB_OK | MB_SERVICE_NOTIFICATION); //GLOK
        }
#endif //_DEBUG

    CString::Format(L"(???+%d)", stringTableID); //GLOK
        return;
    }

    //check for the degenerate case
    if(0 == argsCount)
    {
        CString::operator=(tmp);
        return;
    }

    GetBuffer(tmp.GetLength() * 3); //pre-allocate space
    ReleaseBuffer(0);
    LPCWSTR pStr = tmp;
    while(L'\0' != *pStr)
    {
        bool bSkip = false;

        if(L'{' == *pStr)
        {
            //is this an incoming string position?
            //we only support 10 args, so the next char must be a number
            if(wcschr(L"0123456789", *(pStr + 1))) //GLOK
            {
                if(L'}' == *(pStr + 2)) //and closing brace?
                {
                    bSkip = true;

                    //this is a replacement
                    size_t index = *(pStr + 1) - L'0';
                    _ASSERT(index < argsCount);
                    _ASSERT(index >= 0);
                    if((index >= 0) && (index < argsCount))
                        CString::operator+=(args[index]->ToString());
                    else
                    {
//bad positional index

                        CString msg;
                        msg.Format(L"(??-%d)", index); //GLOK
                        CString::operator+=(msg);
                    }
                    pStr += 2; //get past the two extra characters that we skipped ahead and peeked at
                }
            }
        }

        if(false == bSkip)
            CString::operator+=(*pStr);
        pStr++;
    }
}


CString& String::Format(WORD stringTableID, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    args.push_back(&arg5);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    args.push_back(&arg5);
    args.push_back(&arg6);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    args.push_back(&arg5);
    args.push_back(&arg6);
    args.push_back(&arg7);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    args.push_back(&arg5);
    args.push_back(&arg6);
    args.push_back(&arg7);
    args.push_back(&arg8);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}

CString& String::Format(WORD stringTableID, const StringArg& arg1, const StringArg& arg2, const StringArg& arg3, const StringArg& arg4, const StringArg& arg5, const StringArg& arg6, const StringArg& arg7, const StringArg& arg8, const StringArg& arg9, HINSTANCE hInst)
{
    std::vector<const StringArg*> args;
    args.push_back(&arg1);
    args.push_back(&arg2);
    args.push_back(&arg3);
    args.push_back(&arg4);
    args.push_back(&arg5);
    args.push_back(&arg6);
    args.push_back(&arg7);
    args.push_back(&arg8);
    args.push_back(&arg9);
    CentralFormat(stringTableID, args, hInst);
    return *this;
}
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