Linux c++ .hpp 和 .cpp

c++ .hpp and .cpp

提问by linuxx

Can someone tell me what is the correct way to create a .hpp and .cpp that includes classes, subclasses and methods? Do I have to use export "C" firstClass* create_object { return new firstClass; }? (I am working in C++.) Should I have file.hppor file.h?

有人能告诉我创建包含类、子类和方法的 .hpp 和 .cpp 的正确方法是什么吗？我必须使用export "C" firstClass* create_object { return new firstClass; }吗？（我在 C++ 中工作。）我应该有file.hpp还是file.h？

#include <string>

//public ?? how can i have this?
class firstClass
{
public:
    firstClass();

    class secondClass
    {
    public:
        secondClass();
        std::string name;
        virtual std::string method1();
    } *sec;

    virtual void DoSomething();
} *first;

// And for a private class?

class private *priv;

in file.cpp

在文件.cpp

#include file.hpp
firstClass::firstClass()
{
    sec = new firstClass::secondClass();
}

std::string firstClass::secondClass::method1()
{
    //code
}

And now if I have to externan object for each class/subclass? It is necessary if I want to create an .so file and use dlsym and dlopen to access classes, subclasses and methods, modify values, send a reference to a specific method? Thanks!

现在，如果我必须extern为每个类/子类创建一个对象？如果我想创建一个 .so 文件并使用 dlsym 和 dlopen 来访问类、子类和方法、修改值、发送对特定方法的引用，这是必要的吗？谢谢！

extern "C" firstClass* create_object()
{return new firstClass}
extern "C" secondClass* create_object()
{return new secondClass}

回答by Lstor

Whether you have file.hppor file.his just a matter of preference. Personally, I use .hppto indicate C++ rather than C.

你是否拥有file.hpp或file.h只是一个偏好问题。就个人而言，我习惯于.hpp表示 C++ 而不是 C。

In C++, unlike for example Java, classes in the global namespace are not publicor private. You can, however, hide or limit access to classes in various ways. For example:

在 C++ 中，与 Java 不同，全局命名空间中的类不是public或private。但是，您可以通过各种方式隐藏或限制对类的访问。例如：

• Having them privatein another class.
• Using namespaces.

• 让他们private在另一个班级。
• 使用命名空间。

A few other points:

其他几点：

• The syntax for including file.hppis #include "file.hpp"
• Your firstClassand secondClassclasses have virtual methods and a default destructor. You should make your destructor publicand virtual, or protectedand non-virtual
• Classes are usually defined like this:

• 包含的语法file.hpp是#include "file.hpp"
• 您的firstClass和secondClass类具有虚拟方法和默认析构函数。你应该让你的析构函数publicand virtual, orprotected和 non-virtual
• 类通常是这样定义的：

Class definition:

类定义：

class SomeClass {
    // code
};

and when you want a pointer to it, you write SomeClass* myPointer;, rather than the way you declare firstand sec.

当你想要一个指向它的指针时，你写SomeClass* myPointer;，而不是你声明first和的方式sec。

You usually want to put class declarations and/or definitions in header files, along with function declarations. Implementations goes in the source files. Example:

您通常希望将类声明和/或定义与函数声明一起放在头文件中。实现在源文件中。例子：

// Header file:
class FirstClass {
public:
    FirstClass();
    void DoSomething();
};

// Source file:
FirstClass::FirstClass()
{
    // code
}

void FirstClass::DoSomething()
{
    // code
}

I'd recommend you to pick up a C++ textbook, where such basics are plentifully covered. My personal recommendation is Accelerated C++.

我建议您选择一本 C++ 教科书，其中涵盖了大量此类基础知识。我个人的建议是Accelerated C++。