Question

我正在尝试地图boost::functions。所以我可以通过输入和输出参数的字符串名称来调用它们。

示例：

 MyFuncs::CallFunc("MyClass::TestFunc", void* input, void* output);

我想创建输入和输出变量，并发送指向MyFuncs::CallFunc()的指针进行处理。

我可以将(void* input)指针发送到函数中，并将其值提取到int，string等。

我无法发送一个(void* output)来分配它自己的空间来接收值。我必须在被调用的函数中创建一个new type(var)，否则一旦函数返回，变量就会超出范围。

MyFuncs.h

//MyFuncs.h
#include <boost/function.hpp>
#include <boost/bind.hpp>
#include <map>

class MyFuncs
{
public:

    static std::map<std::string, boost::function<void (void*, void*&)> > myfuncs;

    template<class T>
    static void RegisterFunc(const std::string& name, void (T::*func) (void*, void*&), T* instance)
    {
        myfuncs[name] = boost::bind(func, instance, _1, _2);
    }

    static void CallFunc(const std::string& name, void* input, void*& output)
    {
        myfuncs[name](input, output);
    }
};

std::map<std::string, boost::function<void (void*, void*&)> > MyFuncs::myfuncs;

MyClass.h

//MyClass.h 
#include "MyFuncs.h"

class MyClass
{
public:
    MyClass()
    {
        MyFuncs::RegisterFunc("MyClass::GetNumber",  &MyClass::GetNumber,  this);
        MyFuncs::RegisterFunc("MyClass::GetString",  &MyClass::GetString,  this);
        MyFuncs::RegisterFunc("MyClass::EditNumber", &MyClass::EditNumber, this);
        MyFuncs::RegisterFunc("MyClass::EditString", &MyClass::EditString, this);
    }

    void GetNumber(void* input, void*& output)
    {
        int var = 1234;
        output = static_cast<void*>(new int(var));             //WORKS, var eats memory
        //output = static_cast<void*>(&var);                   //ERROR, var goes out of scope
    }

    void GetString(void* input, void*& output)
    {
        std::string var = "Get test";
        output = static_cast<void*>(new std::string(var));     //WORKS, var eats memory
        //output = static_cast<void*>(&var);                   //ERROR, var goes out of scope
    }

    void EditNumber(void* input, void*& output)
    {
        int var = *static_cast<int*>(input);                   //WORKS, var gets 4321 OK
        output = static_cast<void*>(new int(var));             //WORKS, var eats memory
        //output = static_cast<void*>(&var);                   //ERROR, var goes out of scope
    }

    void EditString(void* input, void*& output)
    {
        std::string var = *static_cast<std::string*>(input);   //WORKS, var gets "Edit test" OK
        output = static_cast<void*>(new std::string(var));     //WORKS, var eats memory
        //output = static_cast<void*>(&var);                   //ERROR, var goes out of scope
    }
};

MyApp.cpp中

//MyApp.cpp 
#include "MyClass.h"

void main()
{
    MyClass myclass;

    void* in;
    void* out;

    MyFuncs::CallFunc("MyClass::GetNumber", NULL, out);  //atempting to fill the variable
    int getNumOut = *static_cast<int*>(out);
    printf("MyClass::GetNumber = %d \n", getNumOut);

    MyFuncs::CallFunc("MyClass::GetString", NULL, out);  //atempting to fill the variable
    std::string getStrOut = *static_cast<std::string*>(out);
    printf("MyClass::GetString = %s \n", getStrOut.c_str());

    int editNum = 4321;
    in = static_cast<void*>(&editNum);
    MyFuncs::CallFunc("MyClass::EditNumber", in, out);  //atempting to fill the variable
    int editNumOut = *static_cast<int*>(out);
    printf("MyClass::EditNumber = %d \n", editNumOut);

    std::string editStr = "Edit test";
    in = static_cast<void*>(&editStr);
    MyFuncs::CallFunc("MyClass::EditString", in, out);  //atempting to fill the variable
    std::string editStrOut = *static_cast<std::string*>(out);
    printf("MyClass::EditString = %s \n", editStrOut.c_str());

    getchar(); //wait for close
}

Answer 1

void* out在main内声明。要使out有效，它应指向其生命周期至少为main的内容。由于您尚未在类int中声明类型string和MyClass的数据成员，这些成员可以通过out返回，因此您需要分配内存。

假设您在类int var;中声明了数据成员MyClass，那么GetNumber将如下所示：

class MyClass
{
    private:
             int var;

    public:
    MyClass()
    {
        //Register function
        var = 10;  
    }

    void GetNumber(void* input, void*& output)
    {
        //int var = 1234;  //<-- instead of using local "var", now use MyClass::var i.e this->var
        output = static_cast<void*>(&(this->var));
    }
};

Answer 2

<强>解
在不使用static_cast或额外的boost函数的情况下，我能够使用纯C ++。

*(int*)output = var;和*(std::string*)output = var;似乎可以解决问题。

的 MyFuncs.h

#include <boost/function.hpp> #include <boost/bind.hpp> #include <map> class MyFuncs { public: //A list of function names linked to boost::functions. static std::map<std::string, boost::function<void (void*, void*)> > myfuncs; //Register a class function by name. MyFuncs::RegisterFunc("MyClass::Test", &MyClass::Test, instance); template<class T> static void RegisterFunc(const std::string& name, void (T::*func) (void*, void*), T* instance) { myfuncs[name] = boost::bind(func, instance, _1, _2); } //Call functions by name, with input and output. MyFunct::CallFunc("MyClass::Test", input, output); static void CallFunc(const std::string& name, void* input, void* output) { myfuncs[name](input, output); } }; std::map<std::string, boost::function<void (void*, void*)> > MyFuncs::myfuncs;

的 MyClass.h

#include "MyFuncs.h" class MyClass { public: MyClass() { MyFuncs::RegisterFunc("MyClass::GetNumber", &MyClass::GetNumber, this); MyFuncs::RegisterFunc("MyClass::GetString", &MyClass::GetString, this); MyFuncs::RegisterFunc("MyClass::EditNumber", &MyClass::EditNumber, this); MyFuncs::RegisterFunc("MyClass::EditString", &MyClass::EditString, this); } void GetNumber(void* input, void* output) { int var = 1234; *(int*)output = var; } void GetString(void* input, void* output) { std::string var = "Get test"; *(std::string*)output = var; } void EditNumber(void* input, void* output) { int in = *(int*)input; //4321 int out = in - 4320; //result is 1; *(int*)output = out; } void EditString(void* input, void* output) { std::string in = *(std::string*)input; //"Edit Test" std::string out = in += " (edited)"; //result is "Edit test (edited)" *(std::string*)output = out; } };

的 MyApp.cpp中

#include "MyClass.h" void main() { MyClass myclass; int getNum; MyFuncs::CallFunc("MyClass::GetNumber", NULL, &getNum); printf("MyClass::GetNumber = %d \n", getNum); std::string getStr; MyFuncs::CallFunc("MyClass::GetString", NULL, &getStr); printf("MyClass::GetString = %s \n", getStr.c_str()); int editNumIn = 4321; int editNumOut; MyFuncs::CallFunc("MyClass::EditNumber", &editNumIn, &editNumOut); printf("MyClass::EditNumber = %d \n", editNumOut); std::string editStrIn = "Edit test"; std::string editStrOut; MyFuncs::CallFunc("MyClass::EditString", &editStrIn, &editStrOut); printf("MyClass::EditString = %s \n", editStrOut.c_str()); getchar(); //wait for close }

将变量发送到void指针或C ++中的void指针引用

2 个答案: