Question

我正在尝试用一些简单的方法创建一个程序，这是我的一个类：

Example.cpp：

#include "Example.hpp"

using namespace std;

ifstream Example::getStream(const char *inputFile) const {
    ifstream myFile;
    myFile.open(inputFile);
    return myFile;
}

Example.hpp：

#include <fstream>
#include <map>

#ifndef EXAMPLE_HPP
#define EXAMPLE_HPP

using namespace std;

class Example {
    public:
        map<int, int> *exampleMap;

    ifstream getStream(const char *inputFile) const;
};

#endif

这是由程序中的其他子类实现的，将来它将非常有用。但是，就目前而言，当我尝试构建它时，它会返回以下错误：

In file included from /usr/include/c++/4.8/ios:42:0,
                 from /usr/include/c++/4.8/istream:38,
                 from /usr/include/c++/4.8/fstream:38,
                 from ../Example.hpp:1,
                 from ../Example.cpp:1:
/usr/include/c++/4.8/bits/ios_base.h: In copy constructor ‘std::basic_ios<char>::basic_ios(const std::basic_ios<char>&)’:
/usr/include/c++/4.8/bits/ios_base.h:786:5: error: ‘std::ios_base::ios_base(const std::ios_base&)’ is private
     ios_base(const ios_base&);
     ^
In file included from /usr/include/c++/4.8/ios:44:0,
                 from /usr/include/c++/4.8/istream:38,
                 from /usr/include/c++/4.8/fstream:38,
                 from ../Example.hpp:1,
                 from ../Example.cpp:1:
/usr/include/c++/4.8/bits/basic_ios.h:66:11: error: within this context
     class basic_ios : public ios_base
           ^
In file included from ../Example.hpp:1:0,
                 from ../Example.cpp:1:
/usr/include/c++/4.8/fstream: In copy constructor ‘std::basic_ifstream<char>::basic_ifstream(const std::basic_ifstream<char>&)’:
/usr/include/c++/4.8/fstream:427:11: note: synthesized method ‘std::basic_ios<char>::basic_ios(const std::basic_ios<char>&)’ first required here 
     class basic_ifstream : public basic_istream<_CharT, _Traits>
           ^
In file included from /usr/include/c++/4.8/ios:43:0,
                 from /usr/include/c++/4.8/istream:38,
                 from /usr/include/c++/4.8/fstream:38,
                 from ../Example.hpp:1,
                 from ../Example.cpp:1:
/usr/include/c++/4.8/streambuf: In copy constructor ‘std::basic_filebuf<char>::basic_filebuf(const std::basic_filebuf<char>&)’:
/usr/include/c++/4.8/streambuf:802:7: error: ‘std::basic_streambuf<_CharT, _Traits>::basic_streambuf(const std::basic_streambuf<_CharT, _Traits>&) [with _CharT = char; _Traits = std::char_traits<char>]’ is private
       basic_streambuf(const basic_streambuf& __sb)
       ^
In file included from ../Example.hpp:1:0,
                 from ../Example.cpp:1:
/usr/include/c++/4.8/fstream:72:11: error: within this context
     class basic_filebuf : public basic_streambuf<_CharT, _Traits>
           ^
/usr/include/c++/4.8/fstream: In copy constructor ‘std::basic_ifstream<char>::basic_ifstream(const std::basic_ifstream<char>&)’:
/usr/include/c++/4.8/fstream:427:11: note: synthesized method ‘std::basic_filebuf<char>::basic_filebuf(const std::basic_filebuf<char>&)’ first required here 
     class basic_ifstream : public basic_istream<_CharT, _Traits>
           ^
../Example.cpp: In member function ‘std::ifstream Example::getStream(const char*) const’:
../Example.cpp:13:12: note: synthesized method ‘std::basic_ifstream<char>::basic_ifstream(const std::basic_ifstream<char>&)’ first required here 
     return myFile;
            ^
make: *** [Example.o] Error 1

我想弄清楚我在这里做错了什么。这是包含的内容吗？这是一些我看不到的拼写错误。

提前致谢。

Answer 1

您正尝试按价值返回流。这在C ++ 11之前是不可能的（并且使用gcc 4.X的标准库实现），因为流不能被复制，而C ++ 98没有移动语义。

所以在C ++ 11中，这段代码很好;如果您的实现尚未完全实现它，则需要一种解决方法，例如传入非const引用，例如：

#ifndef EXAMPLE_HPP #define EXAMPLE_HPP #include <fstream> #include <map> class Example { public: std::map<int, int> *exampleMap; bool openFile(const char *inputFile, std::ifstream &myFile) const; }; #endif

#include "Example.hpp" bool Example::openFile(const char *inputFile, std::ifstream &s) const { myFile.open(inputFile); return myFile.is_open(); }

#include "Example.hpp" Example ex; std::ifstream myFile; if (ex.openFile("filename", myFile)) { //... }

文件I / O错误复制构造函数C ++

1 个答案: