C ++重载输出运算符 [英] C++ overloaded output operator

问题描述

所以我编写我的c ++家庭作业分配，并有一个最后部分，他希望我们用一个重载的输出/插入操作符替换格式化的输出方法（toString）。要100％诚实我不知道他是什么意思。我已经搜索了一下，发现使用重载插入操作符的示例代码，但似乎不能找到如何将它合并到我的代码。虽然我认为我可能在错误的地方看。我的toString如下：

so I am coding my c++ homework assignment and there is a final part where he wants us to Replace the formatted output method (toString) with an overloaded output/insertion operator. TO be 100% honest I have no idea what he means by this. I've searched around a bit and found example codes using an overloaded insertion operator, but can't seem to find how to incorporate it into my code. Though I think I may be looking in the wrong place. My toString is as follows:

string Movie::toString() const {
    ostringstream oS;
    oS << "\n\n====================== Movie Information\n"
    << "\n             Movie Title:\t" << title << "  (" << releaseYear << ")"
    << "\n    US Rank & Box Office:\t" << usRank << "\t$" << usBoxOffice
    << "\nNon-US Rank & Box Office:\t" << nonUSRank << "\t$" << nonUSBoxOffice
    << "\n World Rank & Box Office:\t" << worldRank << "\t$" << worldBoxOffice
    << "\n";
    return oS.str();
}

像我提到的，我不知道什么是overloaded由于某些原因，这不是足够的信息，您可以直接帮助我的问题，那么你可以给我一个简短的描述，他可能是什么意思，用一个重载的输出运算符替换当前的输出。谢谢

Like I mentioned I'm not sure what "overloaded" means, so If for some reason this isn't enough information for you to help me with the problem directly, then can you give me a brief description of what he may mean by replacing the current output with an overloaded output operator. Thank You

编辑：这是我的下一个问题。 C ++重载的输出运算符Cont

edit: This is the next question I have. C++ overloaded output operator Cont

推荐答案

重载函数意味着提供具有相同名称但不同参数类型的其他函数。操作员也可以重载。许多运算符具有可以被重载的相应函数，称为运算符，其中Σ是运算符本身。例如，如果您有两个类 T 的 x 和 y $ c>，可以重载 operator + 。重载操作符允许您为使用该类型的操作符提供一些意义。所以现在你可以做 x + y 。

To overload a function means to provide other functions with the same name but different parameter types. Operators can also be overloaded. Many operators have a corresponding function that can be overloaded called operator??, where ?? is the operator itself. For example if you have two objects x and y of class type T, you could overload operator+. Overloading an operator allows you to give some meaning to using that operator with the type. So now you could do x + y.

流插入操作符 < 。这是你在使用 std :: cin<< hello; - 它插入到流中。此运算符也可以重载，就像 + 上面的重载。您需要重载的函数称为 operator 。

The stream insertion operator is <<. It's what you use when you do std::cin << "hello"; - it inserts into the stream. This operator can also be overloaded, just as + was overloaded above. The function you need to overload is called operator<<.

有两种方法来重载二进制运算符如<< （二进制，因为它需要两个操作数，一个在左侧，一个在右侧， left< / code>）。一个是使它成为 left 类型的成员，并给它一个 right 类型的单个参数。另一个是使它成为具有两个参数的非成员函数，一个类型为 left ，另一个类型为 right 。由于您的左的类型将是 std :: ostream ，您不能修改类（因为它提供

There are two ways to overload a binary operator like << (binary because it takes two operands, one on the left side and one on the right, left << right). One is to make it a member of the type of left and give it a single parameter of the type of right. The other is to make it a non-member function with two parameters, one the type of left and the other the type of right. Since the type of your left will be std::ostream, you can't modify the class (because it's provided by the standard), so you'll have to go with option two.

所以你的自由功能需要看起来像这样：

So your free function needs to look something like this:

std::ostream& operator<<(std::ostream& os, const Movie& movie) {
  // Insert everything you want into `os`
  return os;
}

现在，当您执行 ; <$ / code>在左侧有一个 std :: ostream ，在上有一个 Movie

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