C++之把流对象当做函数参数传递

一、编译不通过的代码：

/*******************************************************************************
* File Name        : ./main.cpp
* Author        : zjw
* Email            : [email protected]
* Create Time    : 2015年04月09日 星期四 17时36分02秒
*******************************************************************************/

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

void Print(ostream out, string strText)
{
    out << strText << endl;
}

int main(int argc, char **argv)
{
    Print(cout, "cout");

    ofstream fout("./test.dat");
    if (!fout.is_open())
    {
        Print(cout, "error");
    }
    else
    {
        Print(fout, "fout");
        fout.close();
    }

    return 0;
}

错误提示：

In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ios:39,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ostream:40,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iostream:40,
                 from ./main.cpp:8:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h: In copy constructor ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h:790: 错误：‘std::ios_base::ios_base(const std::ios_base&)’是私有的
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:47: 错误：在此上下文中
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd: In copy constructor ‘std::basic_ostream<char, std::char_traits<char> >::basic_ostream(const std::basic_ostream<char, std::char_traits<char> >&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:56: 附注：在这里第一次需要生成的方法‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’
./main.cpp: In function ‘int main(int, char**)’:
./main.cpp:21: 附注：在这里第一次需要生成的方法‘std::basic_ostream<char, std::char_traits<char> >::basic_ostream(const std::basic_ostream<char, std::char_traits<char> >&)’
./main.cpp:21: 错误：  初始化‘void Print(std::ostream, std::string)’的实参 1

二、可执行代码：

/*******************************************************************************
* File Name        : ./main.cpp
* Author        : zjw
* Email            : [email protected]
* Create Time    : 2015年04月09日 星期四 17时36分02秒
*******************************************************************************/

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

void Print(ostream &out, string strText)
{
    out << strText << endl;
}

int main(int argc, char **argv)
{
    Print(cout, "cout");

    ofstream fout("./test.dat");
    if (!fout.is_open())
    {
        Print(cout, "error");
    }
    else
    {
        Print(fout, "fout");
        fout.close();
    }

    return 0;
}

编译&执行成功。

三、总结：

这里不明白的是为什么传递流对象不行，而传递引用可以。而且g++的编译错误信息又看不太懂。只能记住以后需要用到流对象做参数，使用传引用了。