类内具有非默认构造函数的类 (C++)

发布于 2024-11-26 07:51:19 字数 919 浏览 1 评论 0原文

我有一个类，它的构造函数有两个参数，一个 int 和一个 void(*)(void) 所以通常当我需要调用它时我会这样做：

obj_child (int_value, pointer_to_foo);

现在我想要的是在另一个类中用常量参数实例化 obj_child 。

所以我尝试了：

class obj_parent
{

    private:

        obj_child child_instantiation (int_value, pointer_to_foo);

};

但这似乎在我声明 child_instantiation 的行上给了我两个编译器错误，所以我猜参数不能传递到那里，而是传递到其他地方。

请注意，child_instantiation 对于所有 obj_parent 实例化应该具有相同的参数，因此不应将它们作为 obj_parent 构造函数参数传递。

声明类指针，然后在堆上创建一个新的指针进行编译，但我不想这样做，而且我不知道它是否有效（我的调试器无法监视引用，因此很难监视这是价值观）。

class obj_parent
    {

        private:

            obj_child *child_instantiation;

    };

obj_parent::
obj_parent (void)
{

    child_instantiation = new obj_child child_instantiation (int_value, pointer_to_foo);


}

谢谢！

（请不要介意语义，子-父与继承无关，只是现在想不出更好的名字）

原文

I have a class which takes two arguments on it's constructor, an int and a void(*)(void) so normally when I need to call it I do it like this:

obj_child (int_value, pointer_to_foo);

Now what I want is to instantiate the obj_child with constant arguments, within another class.

So I tried:

class obj_parent
{

    private:

        obj_child child_instantiation (int_value, pointer_to_foo);

};

but this seems to give me two compiler errors on the line I declare child_instantiation so I guess the arguments can't be passed there but somewhere else.

Mind you child_instantiations are supposed to have the same arguments for all obj_parent instantiations, so they shouldn't be passed as obj_parent constructor arguments.

Declaring the class pointer and then creating a new one on the heap compiles, but I don't want to do it that way and I don't know if it works (my debugger can't watch the reference so it's very hard to monitor it's values).

class obj_parent
    {

        private:

            obj_child *child_instantiation;

    };

obj_parent::
obj_parent (void)
{

    child_instantiation = new obj_child child_instantiation (int_value, pointer_to_foo);


}

Thanks!

(Please don't mind the semantics, child - parent has nothing to do with inheritance, just couldn't think better names right now)

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

标点 2024-12-03 07:51:19

您必须在类的构造函数中初始化该对象。

obj_parent() : child_instantiation (int_value, pointer_to_foo) {}

You have to initialize the object in the constructor of the class.

obj_parent() : child_instantiation (int_value, pointer_to_foo) {}

回复收藏 0 原文

迟到的我 2024-12-03 07:51:19

这是你应该如何做的

// note that this class has no constructor with 0 args
class PrimaryClass {
  public:
    PrimaryClass(int arg1, void* arg2) {
      // do something here
    }
};

class SecondaryClass {
  private:
    PrimaryClass my_obj;
  public:
    // We call the constructor to my_obj here (using initialization lists)
    SecondaryClass(int arg1, void* arg2) : my_obj(arg1, arg2) {
      // other stuff here, maybe
    }
};

Here's how you'd do it

// note that this class has no constructor with 0 args
class PrimaryClass {
  public:
    PrimaryClass(int arg1, void* arg2) {
      // do something here
    }
};

class SecondaryClass {
  private:
    PrimaryClass my_obj;
  public:
    // We call the constructor to my_obj here (using initialization lists)
    SecondaryClass(int arg1, void* arg2) : my_obj(arg1, arg2) {
      // other stuff here, maybe
    }
};

回复收藏 0 原文

~没有更多了~