我可以有一个函数/方法传递一个参数通过引用和一个重载传递它的值在C + +？ [英] Can I have a function/method passing an argument by reference and an overload passing it by value in C++?

问题描述

在C＃中，这当然是可能的，因为这个可编译的例子可以显示：

  static void Teste（int x）{} 
 static void Teste（ref int x）{} 
 static void Teste（）
 {
 int i = 0; 
 Teste（i）; 
 Teste（ref i）; 
} 
  

但是可以用C ++ / CLI）与构造函数？见下面的例子：

  class Foo 
 {
 Foo（int bar）
 { 
 //初始化Foo实例... 
} 
 Foo（int& bar）
 {
 //初始化Foo b $ b} 
 
 // ... 
} 
  

虽然这个类使用这些构造函数编译，我不能看到如何选择何时我应用一个是另一个，也就是调用是ambiguos，因为没有关键字我知道这个目的在C＃中的ref。我在一个构造函数中尝试过，其中名称必须与类相同（当然，我可以添加一个无用的参数，但我想知道是否可以不）。

BTW，我googled只有像通过ref和value之间有什么区别？但没有覆盖这样的重载。我想，作为解决方法，我可以使用指针，感谢取地址（& ）;或者如上所述具有额外的无用参数。

提前感谢，

我想知道的是，

您可以在C ++中完成类似的操作。 >  struct Foo 
 {
 Foo（int / * bar * /）{} 
 Foo（int& / * bar * /）{} 
 }; 
 
 
 int main（）
 {
 int value = 5; 
 Foo foo（static_cast< const int&>（value））; 
 
 return 0; 
} 
  

强制转换为 const 将导致重载解析忽略构造函数接受一个非常量引用，并将通过值。

In C# this is certainly possible, as this compilable example can show:

static void Teste(int x) { }
static void Teste(ref int x) { }
static void Teste()
{
    int i = 0;
    Teste(i);
    Teste(ref i);
}

But can it be done in C++(/CLI) with a constructor? See the example below:

class Foo
{
    Foo(int bar)
    {
        // initializing "Foo" instance...
    }
    Foo(int &bar)
    {
        // initializing "Foo" instance...
    }

    //...
}

Although this class does compile with these constructors I can't see how to choose when I apply one are the other, that is, the call is ambiguos, as there is no keyword I know for this purpose as "ref" in C#. I tried it in a constructor, where the name must be the same as the class (of course I can add a useless parameter, but I want to know if I can not do it).

BTW, I googled and only got things like "what's the difference between passing by ref and by value?" but nothing covering overloading like this. And I guess that as workarounds I can use pointer, thanks to the "take the address of" (&); or have, as mentioned above, an extra useless parameter. But what I want to know is: can I have overloads like these (by ref/by value)?

Thanks in advance,

解决方案

You can accomplish something similar in C++ by providing an explicit cast to the desired type.

struct Foo
{
    Foo(int /*bar*/) {}
    Foo(int &/*bar*/) {}
};


int main()
{
    int value = 5;
    Foo foo(static_cast<const int&>(value));

    return 0;
}

The cast to const will cause overload resolution to ignore the constructor taking a non-const reference and will settle on passing by value.

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