使用模板类时,似乎不包括除main.cpp之外的任何cpp文件 [英] Can't seem to include any cpp file other than main.cpp when using template class
问题描述
我决定将必要的代码削减到显示此错误所需的最低限度。我有一个STL列表包装模板类,它存在于hc_list.h文件中。整个代码如下:
// hc_list.h文件
#ifndef HC_LIST_H
#define HC_LIST_H
#include< cstdlib>
#include< list>
template< typename T>
class hcList
{
private:
std :: list< T> selfList; //一个单一的内部STL列表来保存值
public:
hcList(void){};
〜hcList(void){};
//错误发生在
下面的行template< typename U> friend std :: ostream& operator<<(std :: ostream& const hcList< U>&
};
#endif // HC_LIST_H
此代码包含在main.cpp文件中,其中主要功能如下:
// main.cpp文件
#include< iostream>
#includehc_list.h
int main()
{
std :: cout< 开始测试< std :: endl;
return 0;
}
这段代码,当输入到CodeBlocks项目时,将编译为0错误或警告。但是,我包含另一个cpp文件,并尝试包括列表头,如下所示:
// anyNamedFile.cpp文件
#includehc_list.h
当我将任何cpp文件包含到项目中时,我收到编译器错误:
错误:'&'令牌之前的预期初始化程序
我不明白我做错了什么,真的可以使用一些帮助。
解决方案您的头文件使用
std :: ostream
(& $ c $
code> #include< iosfwd>
。
I decided to cut the necessary code down to the bare minimum needed to display this error. I have an STL list wrapper template class that exists in hc_list.h file. The entire code is below:
// hc_list.h file #ifndef HC_LIST_H #define HC_LIST_H #include <cstdlib> #include <list> template <typename T> class hcList { private: std::list<T> selfList ; // a single internal STL list to hold the values public: hcList(void) {} ; ~hcList(void){} ; // The error occurs on the line below template <typename U> friend std::ostream& operator<<(std::ostream &, const hcList<U> &) ; } ; #endif // HC_LIST_H
This code is included in the main.cpp file, where the main function is below:
// main.cpp file #include <iostream> #include "hc_list.h" int main() { std::cout << "Begin Test" << std::endl; return 0; }
This code, when entered into a CodeBlocks project will compile as is with 0 errors or warnings. However, then I include another cpp file and attempt to include the list header, like the following:
// anyNamedFile.cpp file #include "hc_list.h"
When I include any cpp file into the project, I get a compiler error:
error: expected initializer before '&' token
I do not understand what I am doing wrong, and could really use some help.
解决方案Your header file uses
std::ostream
, (just before an&
) but does not include any header which might declare it.Try adding
#include <iosfwd>
in your header.
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