类的成员函数指针 [英] Class member function pointer

问题描述

我试图用一个类函数（中断服务程序）

I'm trying to use a class function (interrupt service routine),

void (ClassName::*fp)(void)=ClassName::FunctionName;

和其连接到使用与以下类型的输入功能一个Arduino中断引脚，但不起作用。

and attaching it to an Arduino interrupt pin using the function with the following type inputs but that doesn't work.

void attachInterrupt(int, void (*)(void),int);

我怎样才能做到这一点？中断服务程序（ISR）需要访问普里瓦对象数据，所以我不能让课堂之外的功能。

How can I make this happen? The interrupt service routine (ISR) needs to access privat object data, so I can't make a function outside of the class.

我的编译器错误：

ClassName.cpp : : In constructor 'ClassName::ClassName()':
ClassName.cpp : *)()'
ClassName.cpp : *)()' to 'void (*)()' for argument '2' to 'void attachInterrupt(uint8_t, void (*)(), int)'

请注意：我在寻找类中的解决方案，将接受表明我一个解决方案或显示我这是不可能的答案

Note: I am looking for a solution inside the class and will accept the answer that shows me a solution or shows me it's not possible.

推荐答案

如果功能不静态，你不能在输入传递给接受一个非功能-member函数指针。

If the function is not static, you cannot pass it in input to a function that accepts a non-member function pointer.

考虑到非 - 静态成员函数有一个隐含的指针类名作为第一个参数，这点的对象在其上成员函数被调用

Consider that a non-static member function has an implicit pointer to ClassName as its first parameter, which points to the object on which the member function is being invoked.

struct X
{
    static void foo() { } // Does not have an implicit "this" pointer argument
    void bar() { } // Has an implicit "this" pointer argument
};

int main()
{
    void (*f)() = &X::foo; // OK: foo is static
    void (*g)() = &X::bar; // ERROR! bar is non-static
}

在这里，甚至没有的std :: bind（）的将工作，因为结果不是转化为函数指针。 Lambda表达式可以转化为函数指针，但只有当它们是不可捕获（和一个lambda这里需要捕捉对象调用的成员函数）。

Here, not even std::bind() will work, because the result is not convertible to a function pointer. Lambdas are convertible to function pointers, but only if they are non-capturing (and a lambda here would need to capture the object to invoke the member function on).

因此​​，唯一的（丑陋的）解决办法是有它调用一个对象，它可以通过一个全球性的指针变量的成员函数的全局适配器的功能。全局指针变量调用函数之前设置：

Therefore, the only (ugly) workaround is to have a global adapter function which invokes the member function on an object which is available through a global pointer variable. The global pointer variable is set prior to calling the function:

struct X
{
    void bar() { }
};

void function_taking_a_function_pointer(void (*f)())
{
    // Do something...
    f();
}

X* pX = nullptr;
void bar_adapter()
{
    pX->bar();
}

int main()
{
    X x; // Some object I want to invoke the member function bar() on...

    pX = &x; // Set the global pointer and invoke the function...
    function_taking_a_function_pointer(bar_adapter);
}

如果你愿意，你可以让这个稍微灵活转动 bar_adapter 成一个函数的模板的，并通过指针到成员-function作为一个模板参数：

If you want, you can make this slightly more flexible by turning bar_adapter into a function template, and passing the pointer-to-member-function as a template argument:

template<typename T, void (T::*mf)()>
void adapter()
{
    (pX->*mf)();
}

下面是你将如何使用它：

Here is how you would use it:

#include <iostream>

struct X
{
    void foo() { std::cout << "X::foo()" << std::endl; }
    void bar() { std::cout << "X::bar()" << std::endl; }
};

void function_taking_a_function_pointer(void (*f)())
{
    // Do something...
    f();
}

X* pX = nullptr;

template<typename T, void (T::*mf)()>
void adapter()
{
    (pX->*mf)();
}

int main()
{
    X x; // Some object I want to invoke the member function bar() on...

    pX = &x; // Set the global pointer and invoke the function(s)...

    function_taking_a_function_pointer(adapter<X, &X::foo>);
    function_taking_a_function_pointer(adapter<X, &X::bar>);
}

最后，这里是一个活生生的例子。

这篇关于类的成员函数指针的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！