具有按引用传递对象的类会出现编译错误
我在单独的头文件中定义了一个 A 类。我希望 B 类拥有对存储为变量的 A 类对象的引用。
像这样：
文件：Ah
class A {
//Header for class A...
};
文件：Bh
#include "A.h"
class B {
private:
(24) A &variableName;
public:
(36) B(A &varName);
};
当我尝试用 g++ 编译它时，出现以下错误：
B.h:24: error: ‘A’ does not name a type
B.h:36: error: expected `)' before ‘&’ token
关于我做错了什么有什么建议吗？如果重要的话，A 类是一个抽象类。
编辑：代码中的一些拼写错误
I've got a class A defined in a separate header file. I want class B to have a reference to a object of class A stored as a variable.
Like this:
File: A.h
class A {
//Header for class A...
};
File: B.h
#include "A.h"
class B {
private:
(24) A &variableName;
public:
(36) B(A &varName);
};
When i try to compile it with g++ I get the following error:
B.h:24: error: ‘A’ does not name a type
B.h:36: error: expected `)' before ‘&’ token
Any suggestions on what I'm doing wrong? If it matters, the class A is an abstract class.
EDIT: Some typos in the code
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评论（5）
对我来说，它编译得很好（如预期）。我猜
Ah没有被正确包含。是否有另一个同名文件被包含在内？也许有#ifdef 或其他类似的东西会阻止编译器看到A的定义。为了检查这一点，我将某种语法错误放入Ah中，看看编译器是否捕获它。By me it compiles fine (as expected). I'm guessing
A.hisn't being included properly. Is there another file with the same name that gets included instead? Perhaps there are#ifdefs or some such that prevent the definition ofAfrom being seen by the compiler. To check this, I would put some sort of syntax error intoA.hand see if the compiler catches it.Ah 是否包括 Bh（直接或间接）？如果是这样，那么由于递归包含，您将无法在 B 之前定义 A。如果需要在 A 中定义 B，请使用 前向声明。
Does A.h include B.h (directly or indirectly)? If so, then you wouldn't be able to define A before B because of the recursive inclusions. If B needs to be defined in A, use a forward declaration.
您似乎尝试在完全不相关的类 B 中声明类 A 的构造函数，这正是编译器所抱怨的。
如果您希望从编译器的角度使用默认/隐式方式将
B转换为A，您将需要类似的东西而不是构造函数声明。
You appear to try and declare a constructor for class A inside a completely unrelated class B, which is what the compiler is complaining about.
If you want to have default/implicit way of turning a
Binto anAfrom the compiler's perspective, you'll need something likeinstead of a constructor declaration.
据我所知，这段代码是正确的。请检查以下内容：
如果这些都不起作用，那么我无法帮助您，除非您发布发生错误的真实代码。
For all I can see, this code is correct. Check the following please:
If none of these work, well then I cannot help you unless you post the real code where the error happens.
请注意，将引用作为成员变量很少是一个好主意。 B这个名字到底代表什么？
Note that having references as member variables is seldomly a good idea. What does the name B really stand for?