从函数指针数组调用C ++函数 [英] C++ Calling Functions from an Array of Function Pointers

问题描述

我正在使用存储在数组中的函数指针，其中的typedef定义了指针，我对应该如何调用函数有些迷惑.

I'm using function pointers stored in an array with a typedef defining the pointer and I'm a little lost on how I'm supposed to call the function.

这是Menu.h部分:

here's the Menu.h part:

typedef void( Menu::*FunctionPointer )();

FunctionPointer* m_funcPointers;

这是Menu.cpp部分:

here's the Menu.cpp part:

Menu::Menu()
    : m_running( true )
    , m_frameChanged( true )
    , m_currentButton( 0 )
    , m_numOfButtons( k_maxButtons )
    , m_menuButtons( new MenuButton[k_maxButtons] )
    , m_nullBtn( new MenuButton( "null", Vector2( -1, -1 ) ) )
    , m_frameTimer( 0 )
    , m_funcPointers( new FunctionPointer[k_maxButtons])
{
    m_timer.start();
    clearButtons();
    mainMenu();
}

void Menu::enterButton()
{
    m_funcPointers[m_currentButton]();//Error here
}

void Menu::mainMenu()
{
    m_funcPointers[0] = &Menu::btnPlay;
    m_menuButtons[0] = MenuButton("Play", Vector2(0, 0));

    m_funcPointers[1] = &Menu::btnHiScores;
    m_menuButtons[1] = MenuButton("HiScores", Vector2(0, 1));

    m_funcPointers[2] = &Menu::btnExit;
    m_menuButtons[2] = MenuButton("Exit", Vector2(0, 2));
}
void Menu::btnPlay()
{
    StandardGame* game = new StandardGame();

    game->play();

    delete game;
}

m_currentButton是用作索引的整数.我不确定如何实际调用该函数，因为上面的行给了我这个错误:

m_currentButton is an integer used as the index. I'm not sure how to actually call the function as the above line gives me this error:

**C2064 term does not evaluate to a function taking 0 arguments**

视觉工作室给我这个:

expression preceding parentheses of apparent call must have (pointer-to-) function type

我不知道如何解决上述问题，也不知道是由于调用函数还是存储函数.预先感谢.

I don't know how to solve the above problem and whether it's due to how I'm calling the function or how I'm storing it. Thanks in advance.

推荐答案

从函数指针数组中调用函数

Calling Functions from an Array of Function Pointers

以与调用不在数组中的函数相同的方式在数组中调用函数指针.

You call a function pointer in an array the same way as you would call a function that is not in an array.

您的问题不是如何在数组中调用函数指针.您试图像调用成员函数指针那样调用成员函数指针的问题.

Your problem isn't how to call a function pointer in an array as such. Your problem that you're trying to call a member function pointer as if it were a function pointer.

您可以像这样调用成员函数指针:

You can call a member function pointer like this:

Menu menu; // you'll need an instance of the class
(menu.*m_funcPointers[m_currentButton])();

编辑新的示例代码:由于您在成员函数中，因此您可能打算在 this 上调用成员函数指针:

Edit for the new example code: Since you're in a member function, perhaps you intend to call the member function pointer on this:

(this->*m_funcPointers[m_currentButton])();

如果您觉得语法难以阅读，我不会怪您.相反，我建议改用 std :: invoke (自C ++-17起可用):

If you find the syntax painful to read, I won't blame you. Instead, I'll suggest using std::invoke instead (available since C++-17):

std::invoke(m_funcPointers[m_currentButton], this);

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