C++中的对象初始化问题头文件

发布于 2024-10-07 08:10:55 字数 285 浏览 9 评论 0原文

我正在使用 C++ 进行编码，并且类的头文件中有私有数据成员。

private:
      Object1 obj1;
      Object2 obj2(&obj1);

因此，第二个对象采用指向第一个对象的指针。当我尝试编译该程序时，出现以下错误：

“'&' 之前有预期的标识符” token"

有没有办法在实现文件中实例化此类构造函数内的对象而不是其定义？我该如何纠正这个错误？该程序将无法编译。

原文

I am coding in C++, and I have private data members in the header file of a class.

private:
      Object1 obj1;
      Object2 obj2(&obj1);

So, the second object takes a pointer to the first object. When I try to compile the program, I get the following error:

"expected identifier before ‘&’ token"

Is there a way to instantiate the objects inside this class' constructor in the implementation file rather than its definition? How do I correct this error? The program won't compile.

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忘羡 2024-10-14 08:10:55

在 C++ 中，不能将成员初始化作为类定义的一部分。这种操作应该在构造函数中完成：

myClass() : obj2( & (this->obj1) ) { ... }

这通常会生成一个警告，但只要 obj2 在构造 myClass 已完成。

In C++, you cannot initialize members as part of the class definition. This kind of operation should be done in the constructor:

myClass() : obj2( & (this->obj1) ) { ... }

This will usually generate a warning, but will be fine as long as obj2 does not use its constructor argument until the construction of myClass is complete.

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残龙傲雪 2024-10-14 08:10:55

编译器通过此错误告诉您的是，您正在尝试创建一个名为 obj2 的方法，返回一个将引用作为参数的 Object2。但它无法弄清楚引用的类型是什么。

另一方面，如果您想在构造对象之前设置引用，您可以编写如下内容：

Object2* obj2 = &obj1;

编辑

如何纠正此错误？该程序将无法编译。

让你的程序编译并不总是最好的解决方案，也许有一个原因导致它无法编译，你必须理解为什么会这样。仅仅纠正错误可能对您的事业没有帮助。正如 Nawaz 在评论中指出的那样，如果类型 Object1 和 Object2 不同，则您尝试做的事情可能不是正确的事情。

What your compiler is telling you with this error is that you are trying to make a method called obj2, returning an Object2 that is taking a reference as a parameter. But it can't figure out what the type of the reference is.

On the other hand if you want to set the reference before the construction of the object you can write something like this :

Object2* obj2 = &obj1;

Edit

How do I correct this error? The program won't compile.

Making your program compile is not always the best solution, maybe there is a reason why it won't compile and you have to understand why it is so. Simply correcting the error might not help your cause. As Nawaz pointed out in the comment, if the types Object1 and Object2 are different, it is possible that what you are trying to do is not the right thing.

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此岸叶落 2024-10-14 08:10:55

你不能这样写：

 Object2 obj2(&obj1);

使用构造函数来初始化对象，如下所示：

class Sample
{
private:
      Object1 obj1;
      Object2 obj2;
public:
     Sample(Object1 o1)  : obj1(o1), obj2(&o1)
     { 
     }
};

阅读此内容以详细了解这一点：

http://www.cprogramming.com/tutorial/initialization-lists-c++.html

You cannot write like this:

 Object2 obj2(&obj1);

Use constructor to initialize objects, like this:

class Sample
{
private:
      Object1 obj1;
      Object2 obj2;
public:
     Sample(Object1 o1)  : obj1(o1), obj2(&o1)
     { 
     }
};

Read this to understand this in detail:

http://www.cprogramming.com/tutorial/initialization-lists-c++.html

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傲娇萝莉攻 2024-10-14 08:10:55

您不能像声明中那样向成员分配值。您必须在类的构造函数中执行此操作。

MyClass
{
    private:
        Object1 obj1;
        Object2 obj2;

    public:
        MyClass()
        {
            obj2 = Object2(&obj1);
        }
};

You can't assign values to members like that in their declaration. You'll have to do that in the class' constructor.

MyClass
{
    private:
        Object1 obj1;
        Object2 obj2;

    public:
        MyClass()
        {
            obj2 = Object2(&obj1);
        }
};

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