C引用在函数范围内创建的实例

上下文

问题的背景是我正在编写一个与Arduino一起使用的小型库,以便充当游戏控制器.我遇到的问题与C有关,而不是Arduino的具体问题.

我已经在下面包含了库的头文件和源代码,然后是Arduino代码.我尽可能地截断了它.

问题

简而言之,只有我定义的最后一个开关/动作实际上得到了正确的句柄.

这些操作在Arduino设置功能中定义.例如：

controller.addSwitchConTinuous(10,0);  // Pin 10; btn index 0

表示引脚10映射到按钮0.当引脚10关闭时,这被视为按下按钮.这适用于单个动作,但是当我开始添加更多时,只有最后一个动作才有效.因此,在以下示例中,仅识别引脚9：

controller.addSwitchConTinuous(10,0);  // <-- Doesn't work
controller.addSwitchConTinuous(9,1);   // <-- Works

这适用于任意数量的操作：

controller.addSwitchConTinuous(10,1);   // <-- Doesn't work
controller.addSwitchConTinuous(8,2);   // <-- Doesn't work
controller.addSwitchConTinuous(7,3);   // <-- Works

可能的原因

我是C的新手,所以我怀疑我做错了指针.更具体地说,Joystick_实例如何传递似乎有些问题.

我一直在摆弄构造函数并尝试使用引用而不是指针,但我无法让它正常工作.

我可以确认JFSF ::循环中的迭代会迭代所有操作,如果我修改它：

void JFSF::loop()
    {
        for (int n = 0; n < _nextActionIndex; n++)
        {
            if (_actions[n])
            {
                _actions[n]->loop();
                _joystick->setButton(n,PRESSED);  // Debug: Set button pressed,regardless of switch.
            }
        }
        if (_doSendStatE)
        {
            _joystick->sendState();
        }
    }

按钮0到n按预期按下.可能没有正确地调用loop(),但是在这种情况下,我希望N = 1的情况也会失败.此外,最后一个动作总是成功的事实表明迭代是可以的.

完整代码

// JFSF.h
#ifndef JFSF_h
#define JFSF_h

// ... include for Arduino.h and Joystick.h; bunch of defines

namespace JFSF_PRIV
{
class AbstractAction
{
public:
  virtual void loop();
};

/* A Switch that essentially acts as a push button. */
class SwitchConTinuousAction : public AbstractAction
{
public:
  SwitchConTinuousAction(Joystick_ *joystick,int pin,int btnIndeX);
  void loop();

private:
  Joystick_ *_joystick;
  int _pin;
  int _btnIndex;
};

} // namespace JFSF_PRIV

class JFSF
{
public:
  JFSF(Joystick_ *joystick,bool doSendStatE); // doSendState should be true if Joystick_ does not auto send state.
  void loop();
  void addSwitchConTinuous(int inputPin,int btnIndeX);

private:
  Joystick_ *_joystick;
  JFSF_PRIV::AbstractAction *_actions[MAX_ACTIONS];
  int _nextActionIndex;
  bool _doSendState;
};

#endif

源文件(修剪)：

// JFSF.cpp
#include "Arduino.h"
#include "Joystick.h"
#include "JFSF.h"

#define PRESSED 1
#define RELEASED 0

// Private classes
namespace JFSF_PRIV
{

SwitchConTinuousAction::SwitchConTinuousAction(Joystick_ *joystick,int btnIndeX)
{
    _joystick = joystick;
    _pin = pin;
    _btnIndex = btnIndex;
    pinMode(_pin,INPUT_PULLUp);
}

void SwitchConTinuousAction::loop()
{
    int _state = digitalRead(_pin) == LOW ? PRESSED : RELEASED;
    _joystick->setButton(_btnIndex,_statE);
}

} // namespace JFSF_PRIV

JFSF::JFSF(Joystick_ *joystick,bool doSendStatE)
{
    _joystick = joystick;
    _nextActionIndex = 0;
    _doSendState = doSendState;
}

void JFSF::addSwitchConTinuous(int inputPin,int btnIndeX)
{
    JFSF_PRIV::SwitchConTinuousAction newBtnAction(_joystick,inputPin,btnIndeX);
    _actions[_nextActionIndex++] = &newBtnAction;
}

void JFSF::loop()
{
    for (int n = 0; n < _nextActionIndex; n++)
    {
        if (_actions[n])
        {
            _actions[n]->loop();
        }
    }
    if (_doSendStatE)
    {
        _joystick->sendState();
    }
}

为了完整起见,这是Arduino的代码,但它几乎只是声明：

#include <JFSF.h>

// ... A bunch of const declarations used below. these are pretty self explanatory.

// See: https://github.com/MHeironimus/ArduinoJoystickLibrary#joystick-library-api
Joystick_ joystick(HID_REPORT_ID,JOYSTICK_TYPE_JOYSTICK,// _JOYSTICK,_GAMEPAD or _MULTI_AXIS
  BTN_COUNT,HAT_SWITCH_COUNT,INCLUDE_X_AXIS,INCLUDE_Y_AXIS,INCLUDE_Z_AXIS,INCLUDE_RX_AXIS,INCLUDE_RY_AXIS,INCLUDE_RZ_AXIS,INCLUDE_RUDDER,INCLUDE_THROTTLE,INCLUDE_ACCELERATOR,INCLUDE_BRAKE,INCLUDE_STEERING);

JFSF controller(&joystick,!DO_AUTO_SEND_STATE);

void setup() {
  joystick.begin(DO_AUTO_SEND_STATE);
  controller.addSwitchConTinuous(10,0);  // <-- Doesn't work
  controller.addSwitchConTinuous(9,1);   // <-- Works
}

void loop() {
  controller.loop();
}

参考

可以在此处找到ArduinoJoystickLibrary(Joystick_的来源)：https://github.com/MHeironimus/ArduinoJoystickLibrary#joystick-library-api

void JFSF::addSwitchConTinuous(int inputPin,btnIndeX);
    _actions[_nextActionIndex++] = &newBtnAction;
}

void foo(){
    T bar;
    container[index] = &bar;
}