我的程序是评估和表征时间序列信息。数据可能有大约 90 个不同的信号。每个信号都有一个独特的公式和一组不同的参数和值。这段代码和我的问题是从配置文件中加载这些值。编译器是 VS 2010。
每个信号都由一个类表示,这里用 TRI{} 类进行说明,每个这样的类都派生自 SIGNAL{} 类。SIGNAL 包含一个静态映射(我的实际代码使用 unordered_map),它保存成对的信号名称和指向信号成员函数的指针,该函数将参数值分配给它们各自的变量。我的问题是操纵这个成员函数。
显然,信号成员函数的地址,在这段代码 &TRI::load_cfg_vals 中,永远不会存储在映射 sig_map 中。所以从调试器看来。当我尝试调用 TRI 信号的加载函数时,编译器说我正在尝试调用不是函数的东西。请查看我的一些失败尝试的代码。
我怎样才能让它与这些对象一起工作?我真的不知道问题是什么,更糟糕的是,我不知道我对如何使用 STL 或 C++ 不了解。
(我准备放弃了。我正在考虑另一种更类似于 C 的方法。使用映射,将每个信号名称与一个唯一的整数相关联(已经在实际代码中 - 它们都表示为唯一的单个bits). 将 void 指针数组的每个元素加载到该元素数组中的整数值是偏移量的信号的加载函数的地址。我选择的第一种方式,下面的代码,似乎更容易维护,更高级一点。)
在发布之前我研究的许多问题和答案中
TIA
#include <iostream>
#include <map>
#include <string>
using namespace std;
typedef std::map< string, void *> ARG_MAP;
typedef ARG_MAP::iterator ARG_ITR;
typedef std::pair < ARG_ITR, bool> ARG_PAIR;
// forward decl
class SIGNAL;
typedef int (SIGNAL::*PF)(void);
typedef std::map< string, PF> SIG_MAP;
typedef SIG_MAP::iterator SIG_MAP_ITR;
typedef std::pair < SIG_MAP_ITR, bool> SIG_MAP_PAIR;
class SIGNAL
{
public:
ARG_MAP arg_map;
ARG_ITR ai;
ARG_PAIR ap;
static SIG_MAP sig_map;
SIGNAL() {};
~SIGNAL(){};
virtual int calc() = 0;
virtual int load_cfg_vals() = 0;
};
// tried globals versus members, no difference
SIG_MAP SIGNAL::sig_map;
SIG_MAP_ITR smi;
SIG_MAP_PAIR smp;
class TRI: public SIGNAL
{
public:
float f;
int calc(){return 1;}
int load_cfg_vals()
{
// the f arg
ai = arg_map.find("f_descriptive_name");
*(float *) ai->second = (float)12.005;
return 1;
};
TRI()
{
// associates the TRI class function 'load_cfg_vals()' with the
// signal name 'tri'
SIGNAL::sig_map.insert(std::make_pair ("tri",
(PF) &TRI::load_cfg_vals));
// this apparently doesn't load the address of the function, see below
//sig_map.insert(std::make_pair ("tri",&TRI::load_cfg_vals));
// fails with error C2440: 'initializing' : cannot convert from
// from 'int (__thiscall TRI::* )(void)' to 'PF '
//SIGNAL::sig_map.insert( map<string, PF>::value_type("tri",
// dynamic_cast< & SIGNAL::load_cfg_vals> (&TRI::load_cfg_vals) ));
// C2059: syntax error : '&'
// so, maybe this is right but for my lack of understanding of what
// types are involved/required here
// contains the list of descriptive names of the signal's parameters
// and the addresses of the variables that hold the parameters'values
arg_map.insert(std::make_pair ("f_descriptive_name", (void*) &f));
};
~TRI(){};
};
int main(void)
{
TRI tri;
PF pf;
char * input_str = "tri"; // this and the names of the many other
// signals would be read from the cfg file
// while there are still more signal names to read in
// while( fscanf(...input_str...) { removed
if( (smi = tri.sig_map.find (input_str)) == tri.sig_map.end())
cout << "'" << input_str << "' not found\n";
else
{
// smi->second is supposed to contain the function of the
// signal class that is to properly interpret and handle
// the list of values stored in the cfg file
//(smi->second)();
// error C2064: term does not evaluate to a function taking
// 0 arguments
string s = smi->first; // OK
pf = (PF)smi->second;
// Doesn't contain the address of the function that was
// loaded, above, in TRI(). The debugger identifies
// it as TRI::`vcall'{4}', I don't know what that is.
// Debugger emits the entire type of the operator and
// its return value, but I can't get it to format for
// proper display here. If someone wants to see it,
// I'll supply it unformatted.
//int z = (*pf)();
// error C2064: term does not evaluate to a function taking 0
// arguments
// the following don't help the value in pf. same error C2064 or
// complaints about improper use of the casts
//pf = reinterpret_cast <int (__thiscall *)(void)>(smi->second);
//pf = static_cast <int (__thiscall *)(void)>(smi->second);
}
// } // end while removed
return 1;
}