STL - C++ "no matching function for call to"结构错误

Question

我有将 GUID(unsigned long) 映射到结构的 C++ 代码。

#include <string>
#include <map>
#include <iostream>

typedef unsigned long GUID;

enum Function {
  ADDER = 1,
  SUBTRACTOR = 2,
  MULTIPLIER = 3,
  SQUAREROOT = 4
};

struct PluginInfo
{
    GUID guid;
    std::string name;
    Function function;

    PluginInfo(GUID _guid, std::string _name, Function _function) {guid = _guid, name = _name, function = _function;}
};

typedef std::map<GUID, PluginInfo> PluginDB;

PluginInfo temp1(1, "Adder", ADDER);
PluginInfo temp2(2, "Multiplier", MULTIPLIER);

PluginDB::value_type pluginDbArray[] = {
    PluginDB::value_type(1, temp1),
    PluginDB::value_type(2, temp2)
};

const int numElems = sizeof pluginDbArray / sizeof pluginDbArray[0];
PluginDB pluginDB(pluginDbArray, pluginDbArray + numElems);

int main()
{
    std::cout << pluginDB[1].name << std::endl;
}

当我编译它时，我收到错误消息。

/usr/include/c++/4.2.1/bits/stl_map.h: In member function ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = long unsigned int, _Tp = PluginInfo, _Compare = std::less, _Alloc = std::allocator >]’: mockup_api.cpp:58: instantiated from here /usr/include/c++/4.2.1/bits/stl_map.h:350: error: no matching function for call to ‘PluginInfo::PluginInfo()’ mockup_api.cpp:29: note: candidates are: PluginInfo::PluginInfo(GUID, std::string, Function) mockup_api.cpp:24: note:
PluginInfo::PluginInfo(const PluginInfo&)

可能出了什么问题？

Answer 1

您放置在用初始数量的对象初始化的 STL 容器中的任何对象(即，您没有初始化一个空容器)都必须至少有一个默认构造函数...您的没有。换句话说，您当前的构造函数需要使用特定对象进行初始化。必须有一个默认构造函数，如下所示:

PluginInfo();

不需要初始化器。或者，它们可以是默认初始化程序，例如:

PluginInfo(GUID _guid = GUID(), 
           std::string _name = std::string(), 
           Function _function = Function()): 
           guid(_guid), name(_name), function(_function) {}