C ++ - 错误：没有匹配函数来调用'Motor :: Motor（）'

Question

i have a problem with my code.

I have two errors :

Fist error :

MotorManager.cpp:7: error: no matching function for call to 'Motor::Motor()'

Second error :

MotorManager.cpp:10: error: use of deleted function 'Motor& Motor::operator=(Motor&&)'

MotorManager.cpp

#include "MotorManager.h"
#include "Pins.h"
#include "Direction.h"
#include "Motor.h"

MotorManager::MotorManager() {

  // Init motors
  _motorLeftFront = Motor(MOTOR_FRONT_LEFT_FORWARD, MOTOR_FRONT_LEFT_BACKWARD);
  _motorRightFront = Motor(MOTOR_FRONT_RIGHT_FORWARD, MOTOR_FRONT_RIGHT_BACKWARD);
  _motorLeftBack = Motor(MOTOR_BACK_LEFT_FORWARD, MOTOR_BACK_LEFT_BACKWARD);
  _motorRightBack = Motor(MOTOR_BACK_RIGHT_FORWARD, MOTOR_BACK_RIGHT_BACKWARD);
}

MotorManager.h

#include "Pins.h"
#include "Direction.h"
#include "Motor.h"

class MotorManager {
public:

  // Constuctor
  MotorManager();
};

Motor.cpp

#include "Motor.h"
#include "Direction.h"

Motor::Motor(const int pinForwad, const int pinBackward) : _pinForwad(pinForwad), _pinBackward(pinBackward) {

    pinMode(pinForwad, OUTPUT);
    pinMode(pinBackward, OUTPUT);
}

Motor.h

#include "Direction.h"

class Motor {
public:

    // Constructor
    Motor(const int pinForwad, const int pinBackward);
private:
//Variables
int _pinForwad;
int _pinBackward;
};

Thanks

Answer 1

When an instance of MotorManager is constructed, the compiler needs to initialize all of its member variables as well. Since the members aren't initialized in the initializer list, it attempts to call the default constructor for the class. Since Motor doesn't have a default constructor, you get the error.

This can be fixed by initializing the member variables in the initializer list:

MotorManager::MotorManager()
: _motorLeftFront(MOTOR_FRONT_LEFT_FORWARD, MOTOR_FRONT_LEFT_BACKWARD),
  _motorRightFront(MOTOR_FRONT_RIGHT_FORWARD, MOTOR_FRONT_RIGHT_BACKWARD),
  _motorLeftBackMOTOR_BACK_LEFT_FORWARD, MOTOR_BACK_LEFT_BACKWARD),
  _motorRightBack(MOTOR_BACK_RIGHT_FORWARD, MOTOR_BACK_RIGHT_BACKWARD)
{
}

Answer 2

The primary problem is, that you'll need to use the member initializer list in the constructor definition, because otherwise MotorManager wants to initialize them with the default constructor.

You can fix it like this:

MotorManager::MotorManager() 
    : _motorLeftFront(MOTOR_FRONT_LEFT_FORWARD, MOTOR_FRONT_LEFT_BACKWARD)
    , _motorRightFront(MOTOR_FRONT_RIGHT_FORWARD, MOTOR_FRONT_RIGHT_BACKWARD)
    , _motorLeftBack(MOTOR_BACK_LEFT_FORWARD, MOTOR_BACK_LEFT_BACKWARD)
    , _motorRightBack(MOTOR_BACK_RIGHT_FORWARD, MOTOR_BACK_RIGHT_BACKWARD)
{}

---

  MotorManager.cpp:10: error: use of deleted function 'Motor& Motor::operator=(Motor&&)' 

That's a follow up error because you used assignment statements

  _motorLeftFront = Motor(MOTOR_FRONT_LEFT_FORWARD, MOTOR_FRONT_LEFT_BACKWARD);

but didn't declare a move assignment operator overload like:

Motor& Motor::operator=(Motor&&) = default;

or at least copy assignment:

Motor& Motor::operator=(const Motor&) = default;