C ++类继承，对基类成员函数的未定义引用

时间：2018-11-27 10:39:15

标签： c++ inheritance

我只是在学习c ++，并且在继承方面遇到了麻烦，从c＃的背景开始，我感到C ++的继承性要复杂一些。

我有一个具有虚拟和纯虚拟方法的基类UserInterface：

class UserInterface
{
 protected:
    LiquidCrystal* lcd;

const int ICON_WATER_DROP = 0;
const int ICON_SMILEY = 1;
const int ICON_STATION = 2;
const int ICON_WATER_DROPS = 3;
const int ICON_ALARM = 4;
const int ICON_PRESSURE = 5;

/* icon for water drop */
byte waterDrop[8] =
{
        B00100,
        B00100,
        B01010,
        B01010,
        B10001,
        B10001,
        B10001,
        B01110
};

byte bucket[8] =
{
        B01010,
        B00100,
        B00010,
        B11111,
        B10001,
        B11111,
        B10001,
        B11111
};

/* smiley face */
byte smiley[8] =
{
        B00000,
        B10001,
        B00000,
        B00000,
        B10001,
        B01110,
        B00000,
        B00000
};

byte station[8] =
{
        B11110,
        B10010,
        B11111,
        B10011,
        B10011,
        B10011,
        B10010,
        B11111
};

byte alarm[8] =
{
        B00000,
        B00100,
        B01110,
        B01110,
        B01110,
        B11111,
        B00100,
        B00000
};

byte pressure[8] =
{
        B00100,
        B01110,
        B11111,
        B00100,
        B00100,
        B11111,
        B01110,
        B00100
};
public:
UserInterface();
virtual ~UserInterface();

virtual void drawIcon(int icon);
virtual void drawInitializingScreen();
virtual void clearScreen();
virtual void drawText(const __FlashStringHelper *line1);
virtual void drawText(const __FlashStringHelper *line1, const __FlashStringHelper *line2);
virtual void drawText(const __FlashStringHelper *line1, int line2);
virtual void drawAddressSetupScreen(int address);

// All this methods need to be implemented by each subclass
virtual void drawHomeScreen(byte address) = 0;
virtual void drawWateringTotalVolumeScreen(char* remainingTime, char* litres) = 0;
virtual void drawWateringVolumePerMinuteScreen(char* remainingTime, char* litres) = 0;
virtual void drawWateringPressureScreen(char* remainingTime, char* presure) = 0;
virtual void drawWateringPausedScreen(char* remainingTime) = 0;
virtual void drawWateringPausedAlternateScreen(char* remainingTime) = 0;
virtual void drawOutOfService(byte address) = 0;
virtual void drawInvalidSelection() = 0;
};

和类实现：

   UserInterface::UserInterface()
{
    //lcd = new LiquidCrystal(12, 11, 5, 4, 3, 2);
    lcd = new LiquidCrystal(5, 6, 7, 8, 9, 10);
    lcd->clear();

    // create a new custom characters
    lcd->createChar(ICON_WATER_DROP, waterDrop);
    lcd->createChar(ICON_SMILEY, smiley);
    lcd->createChar(ICON_STATION, station);
    lcd->createChar(ICON_WATER_DROPS, bucket);
    lcd->createChar(ICON_ALARM, alarm);
    lcd->createChar(ICON_PRESSURE, pressure);
}

UserInterface::~UserInterface()
{

}

void UserInterface::drawIcon(int icon)
{
    // print the custom char to the lcd
    lcd->write(icon);
}

void UserInterface::drawInitializingScreen()
{
    lcd->setCursor(0, 0);
    lcd->print(F("INICIALIZANDO"));
    lcd->setCursor(0, 1);
    lcd->print(F("VER:"));
    lcd->setCursor(5, 1);
    lcd->print(__DATE__);
}

void UserInterface::clearScreen()
{
    lcd->clear();
}

void UserInterface::drawText(const __FlashStringHelper *line1)
{
    lcd->setCursor(0, 0);
    lcd->print(line1);
}

void UserInterface::drawText(const __FlashStringHelper *line1, const __FlashStringHelper *line2)
{
    lcd->setCursor(0, 0);
    lcd->print(line1);
    lcd->setCursor(0, 1);
    lcd->print(line2);
}

void UserInterface::drawText(const __FlashStringHelper *line1, int line2)
{
    lcd->setCursor(0, 0);
    lcd->print(line1);
    lcd->setCursor(0, 1);
    lcd->print(line2);
}

void UserInterface::drawAddressSetupScreen(int address)
{
    lcd->setCursor(0, 0);
    lcd->print(F("ADDRESS SETUP"));
    lcd->setCursor(0, 1);
    lcd->print(address);
}

和一个子类：

class LCD16x2: public UserInterface
{
public:
    LCD16x2();
    ~LCD16x2();

    void drawIcon(int icon);
    void drawInitializingScreen();
    void clearScreen();
    void drawText(const __FlashStringHelper *line1);
    void drawText(const __FlashStringHelper *line1, const __FlashStringHelper *line2);
    void drawText(const __FlashStringHelper *line1, int line2);
    void drawAddressSetupScreen(int address);

    // All this methods need to be implemented by each subclass
    void drawHomeScreen(byte address) override;
    void drawWateringTotalVolumeScreen(char* remainingTime, char* litres) override;
    void drawWateringVolumePerMinuteScreen(char* remainingTime, char* litres) override;
    void drawWateringPressureScreen(char* remainingTime, char* presure) override;
    void drawWateringPausedScreen(char* remainingTime) override;
    void drawWateringPausedAlternateScreen(char* remainingTime) override;
    void drawOutOfService(byte address) override;
    void drawInvalidSelection() override;
};

和实现：

LCD16x2::LCD16x2()
{
    lcd->begin(16, 2);
}

LCD16x2::~LCD16x2()
{

}

void LCD16x2::drawHomeScreen(byte address)
{
    lcd->setCursor(0, 0);
    lcd->print(" HUERTOS DE OCIO");

    lcd->setCursor(0, 1);
    lcd->write(ICON_STATION);

    lcd->setCursor(3, 1);
    lcd->print(F("ESTACION "));
    lcd->print(address);
}

void LCD16x2::drawWateringTotalVolumeScreen(char* remainingTime, char* volume)
{
    lcd->setCursor(0, 0);
    lcd->print(F("RIEGO EN CURSO"));

    lcd->setCursor(0, 1);
    lcd->write(ICON_ALARM);
    lcd->setCursor(1, 1);
    lcd->print(remainingTime);

    lcd->setCursor(10, 1);
    lcd->write(ICON_WATER_DROP);
    lcd->setCursor(11, 1);
    lcd->print(volume);
}

void LCD16x2::drawWateringVolumePerMinuteScreen(char* remainingTime,
        char* volumePerMinute)
{
    lcd->setCursor(0, 0);
    lcd->print(F("RIEGO EN CURSO"));

    lcd->setCursor(0, 1);
    lcd->write(ICON_ALARM);
    lcd->setCursor(1, 1);
    lcd->print(remainingTime);

    lcd->setCursor(10, 1);
    lcd->write(ICON_WATER_DROPS);
    lcd->setCursor(11, 1);
    lcd->print(volumePerMinute);
}

void LCD16x2::drawWateringPressureScreen(char* remainingTime, char* pressure)
{
    lcd->setCursor(0, 0);
    lcd->print(F("RIEGO EN CURSO"));

    lcd->setCursor(0, 1);
    lcd->write(ICON_ALARM);
    lcd->setCursor(1, 1);
    lcd->print(remainingTime);

    lcd->setCursor(10, 1);
    lcd->write(ICON_PRESSURE);
    lcd->setCursor(11, 1);
    lcd->print(pressure);
}

void LCD16x2::drawWateringPausedScreen(char* remainingTime)
{
    lcd->setCursor(0, 0);
    lcd->print(F("RIEGO EN PAUSA"));
    lcd->setCursor(0, 1);
    lcd->print(remainingTime);
}

void LCD16x2::drawWateringPausedAlternateScreen(char* remainingTime)
{
    drawWateringPausedScreen(remainingTime);
}

void LCD16x2::drawOutOfService(byte address)
{
    lcd->setCursor(3, 0);
    lcd->print(F("ESTACION "));
    lcd->print(address);
    lcd->setCursor(0, 1);
    lcd->print(F("FUERA DE SERVICIO"));
}

void LCD16x2::drawInvalidSelection()
{
    lcd->setCursor(0, 1);
    lcd->print(F("SELECCION"));
    lcd->setCursor(0, 2);
    lcd->print(F("INVALIDA"));
}

问题是编译器似乎无法接受对基类中实现的虚拟方法的调用：

C：\ Users \ marcp \ AppData \ Local \ Temp \ ccjzyoeN.ltrans2.ltrans.o :(。rodata + 0x8e）：对LCD16x2::drawIcon(int)' C:\Users\marcp\AppData\Local\Temp\ccjzyoeN.ltrans2.ltrans.o:(.rodata+0x90): undefined reference to LCD16x2 :: drawInitializingScreen（）的未定义引用 C：\ Users \ marcp \ AppData \ Local \ Temp \ ccjzyoeN.ltrans2.ltrans.o :(。rodata + 0x92）：对LCD16x2::clearScreen()' C:\Users\marcp\AppData\Local\Temp\ccjzyoeN.ltrans2.ltrans.o:(.rodata+0x94): undefined reference to LCD16x2 :: drawText（__ FlashStringHelper const *）的未定义引用 C：\ Users \ marcp \ AppData \ Local \ Temp \ ccjzyoeN.ltrans2.ltrans.o :(。rodata + 0x96）：对LCD16x2::drawText(__FlashStringHelper const*, __FlashStringHelper const*)' C:\Users\marcp\AppData\Local\Temp\ccjzyoeN.ltrans2.ltrans.o:(.rodata+0x98): undefined reference to LCD16x2 :: drawText（__ FlashStringHelper const *，int）的未定义引用” C：\ Users \ marcp \ AppData \ Local \ Temp \ ccjzyoeN.ltrans2.ltrans.o :(。rodata + 0x9a）：对LCD16x2::drawAddressSetupScreen(int)' C:\Users\marcp\AppData\Local\Temp\ccjzyoeN.ltrans3.ltrans.o: In function updateFirmwareCommand的未定义引用（无符号字符*，无符号字符*，无符号字符*） '： C：\ Users \ marcp \ Dropbox \ Source \ RiegoMatic \ HDO.RiegoMatic.Station.Firmware \ Release / .. \ RMStationFirmware.cpp：1149：对LCD16x2::clearScreen()' C:\Users\marcp\Dropbox\Source\RiegoMatic\HDO.RiegoMatic.Station.Firmware\Release/..\RMStationFirmware.cpp:1152: undefined reference to LCD16x2 :: drawText（__ FlashStringHelper const *，__FlashStringHelper的未定义引用const *）' C：\ Users \ marcp \ AppData \ Local \ Temp \ ccjzyoeN.ltrans3.ltrans.o：在函数selfTest': C:\Users\marcp\Dropbox\Source\RiegoMatic\HDO.RiegoMatic.Station.Firmware\Release/..\RMStationFirmware.cpp:693: undefined reference to LCD16x2 :: clearScreen（）'中 C：\ Users \ marcp \ Dropbox \ Source \ RiegoMatic \ HDO.RiegoMatic.Station.Firmware \ Release / .. \ RMStationFirmware.cpp：704：对LCD16x2::drawText(__FlashStringHelper const*, int)' C:\Users\marcp\AppData\Local\Temp\ccjzyoeN.ltrans3.ltrans.o: In function updateLCD（bool）'的未定义引用： C：\ Users \ marcp \ Dropbox \ Source \ RiegoMatic \ HDO.RiegoMatic.Station.Firmware \ Release / .. \ RMStationFirmware.cpp：160：对LCD16x2::clearScreen()' C:\Users\marcp\Dropbox\Source\RiegoMatic\HDO.RiegoMatic.Station.Firmware\Release/..\RMStationFirmware.cpp:169: undefined reference to LCD16x2 :: drawInitializingScreen（）的未定义引用 collect2.exe：错误：ld返回1退出状态 makefile：89：目标“ RMStationFirmware.elf”的配方失败 制作：*** [RMStationFirmware.elf]错误1

1 个答案:

答案 0 :(得分：1)

  1. ~LCD16x2()应该是虚拟的。
  2. 如果不打算覆盖派生类中的方法，则不要在其上重新声明这些方法。只需从LCD16x2中删除它们的声明即可。如果要覆盖，请在基类和派生类中将它们声明为虚拟的。
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