将ifstream作为参数传递给Class Constructor [英] Passing ifstream as an argument to Class Constructor

问题描述

在我的main（）中，被称为FIFO的类的构造函数：FIFO（infile）;

在FIFO（FIFO.h）的头文件中，我有：

  FIFO（std :: ifstream）; 
 std :: ifstream infile; 
  

在FIFO.cc中，我有：

  FIFO :: FIFO（std :: ifstream& INFILE）
 {
 infile = INFILE; 
} 
  

我不断变得喜欢（有更多的，我只是粘贴一个他们）：

在/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../中包含的文件中/include/c++/4.4.7/bits/localefwd.h:43，
来自/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../ .. /include/c++/4.4.7/string:45，
from FIFO.cc:7：
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../ .. /../../include/c++/4.4.7/bits/ios_base.h：在成员函数'std :: basic_ios>& std :: basic_ios> :: operator =（const std :: basic_ios>&）'：
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../ .. /../include/c++/4.4.7/bits/ios_base.h:793：error：'std :: ios_base& std :: ios_base :: operator =（const std :: ios_base&）'是private
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../。 ./include/c++/4.4.7/iosfwd:47：错误：在此上下文中

我不知道如果传递ifstream使用引用是否工作，我的代码问题。

谢谢！

解决方案

在构造函数声明中， std :: ifstream 按值而不是引用。而不是

  FIFO（std :: ifstream）; 
  

应为

  FIFO（std :: ifstream&）; 
  

，并且通过值而不是引用存储成员变量'infile'。

  std :: ifstream infile; 
  

应为

  std :: ifstream&英语：infile; 
  

由于您现在存储对ifstream的引用，因此您需要在初始化程序列表而不是在构造函数中分配。

  FIFO :: FIFO（std :: ifstream& INFILE） 
：infile（INFILE）
 {
} 
  

因为 std :: ifstream 的复制构造函数是私有的（或在C ++ 11中删除）。通过按值存储成员变量，您试图复制传递给构造函数的 std :: ifstream 对象。

I am trying to pass: ifstream infile;

in my main (), to the constructor of a class called "FIFO": FIFO (infile);

In the header file of FIFO (FIFO.h), I have:

FIFO (std::ifstream);
std::ifstream infile;

And in FIFO.cc, I have:

FIFO::FIFO (std::ifstream & INFILE)
{
         infile = INFILE;
}

I kept getting like (There are more of them, I just paste one of them):

In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/localefwd.h:43, from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/string:45, from FIFO.cc:7: /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ios_base.h: In member function ‘std::basic_ios >& std::basic_ios >::operator=(const std::basic_ios >&)’: /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ios_base.h:793: error: ‘std::ios_base& std::ios_base::operator=(const std::ios_base&)’ is private /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:47: error: within this context

I am not sure if passing ifstream using reference works or not, or it is my codes problem.

Thanks!

解决方案

In your constructors declaration you are taking the std::ifstream by value instead of by reference. Instead of

FIFO (std::ifstream);

it should be

FIFO (std::ifstream&);

and you are storing the member variable 'infile' by value instead of by reference.

std::ifstream infile;

should be

std::ifstream& infile;

Since you are now storing a reference to the ifstream you need to initialize it in the initializer list instead of assigning it in the constructor.

FIFO::FIFO (std::ifstream & INFILE)
    : infile(INFILE)
{
}

This is because the copy constructor of std::ifstream is private (or deleted in C++11). By storing the member variable by value you are attempting to make a copy of the std::ifstream object passed to the constructor.

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