抽象类和构造函数

Question

我们正在尝试在 C++ 中使用抽象超级class 实现一个解决方案： Control是Spline等的超class。现在，当我们尝试实例化 Spline 类型的对象时，实例化失败并出现两个错误：

cannot find method with matching parameters for the constructor of class Spline

cannot allocate an object of abstract type 'Control'

我们如何解决这些问题？

实例化Control类型的Spline并在main中使用它：

RampFunction timeRampFn{0, 100, 2000, 1000};
RampFunction distanceRampFn{0, 0, 0.5f, 1000};

Control ctrl = new Spline(slowDownCoeff, timeRampFn, distanceRampFn);

ctrl.calculateAction(&newRobotState, p_0, p_t, targetTrack, timeFromStart, distanceToTarget);

Control.hpp（抽象超class）：

#ifndef CONTROL_HPP
#define CONTROL_HPP

#include <vector>
#include <Data/Track.h>
#include <Data/TrackPoint.h>
#include <Data/RobotState.h>
#include <boost/multiprecision/eigen.hpp>

using Eigen::Vector2f;
using namespace std;

class Control
{
private:
const float FUTURE_INTERVAL = 0.1f;

protected:
const int FUTURE_SIZE = 10;

public:
virtual void calculateAction(RobotState *state, Vector2f curPos, Vector2f refPos, Track targetTrack, float timeFromStart, float distanceToTarget) = 0;
};

#endif

Spline.hpp:

#ifndef SPLINE_HPP
#define SPLINE_HPP

#include <Control/Control.hpp>

using Eigen::Vector2f;
using namespace std;

class Spline : Control
{
private:
struct RampFunction
{
    float x_0, val_0;
    float x_e, val_e;
};
float slowDownCoeff;
RampFunction timeRampFn;
RampFunction distanceRampFn;

public:
Spline(float slowDownCoeff, RampFunction timeRampFn, RampFunction distanceRampFn)
{
    this->slowDownCoeff = slowDownCoeff;
    this->timeRampFn = timeRampFn;
    this->distanceRampFn = distanceRampFn;
}
virtual void calculateAction(RobotState *state, Vector2f curPos, Vector2f refPos, Track targetTrack, float timeFromStart, float distanceToTarget);
};

#endif

Answer 1

Control ctrl = ...

您创建了一个 Control 类型的变量。这是不允许的，因为 Control 是抽象类型。这就是您收到错误 cannot allocate an object of abstract type 'Control'.

的原因

另一个问题是 Control 没有接受类型为 Spline* 的参数的构造函数。

您可能一直在尝试创建一个指向派生对象的基指针：Control* ctrl = ...。但是，这会使删除动态分配有问题，因为不允许通过基指针进行删除，因为基的析构函数是非虚拟的。一种解决方案是将析构函数声明为虚拟的。

但仅仅允许删除是不够的。您应该实际执行删除，否则内存可能会泄漏。

Answer 2

这应该是您想要的修改后的代码。

main.cpp

RampFunction timeRampFn{0, 100, 2000, 1000};
RampFunction distanceRampFn{0, 0, 0.5f, 1000};

Control *ctrl = new Spline(slowDownCoeff, timeRampFn, distanceRampFn);

ctrl->calculateAction(&newRobotState, p_0, p_t, targetTrack, timeFromStart, 
distanceToTarget);

Control.hpp

#ifndef CONTROL_HPP
#define CONTROL_HPP

#include <vector>
#include <Data/Track.h>
#include <Data/TrackPoint.h>
#include <Data/RobotState.h>
#include <boost/multiprecision/eigen.hpp>

using Eigen::Vector2f;
using namespace std;

class Control
{
private:
const float FUTURE_INTERVAL = 0.1f;

protected:
const int FUTURE_SIZE = 10;

public:
virtual ~Control() {}
virtual void calculateAction(RobotState *state, Vector2f curPos, Vector2f refPos, Track targetTrack, float timeFromStart, float distanceToTarget) = 0;
};

#endif

Spline.hpp

#ifndef SPLINE_HPP
#define SPLINE_HPP

#include <Control/Control.hpp>

using Eigen::Vector2f;
using namespace std;

class Spline : Control
{
private:
struct RampFunction
{
    float x_0, val_0;
    float x_e, val_e;
};
float slowDownCoeff;
RampFunction timeRampFn;
RampFunction distanceRampFn;

public:
Spline(float slowDownCoeff, RampFunction timeRampFn, RampFunction distanceRampFn)
: slowDownCoeff(slowDownCoeff), timeRampFn(timeRampFn), distanceRampFn(distanceRampFn) {}

virtual void calculateAction(RobotState *state, Vector2f curPos, Vector2f refPos, Track targetTrack, float timeFromStart, float distanceToTarget);
};

#endif

抽象类和构造函数

Abstract classes and constructor

c++

abstract-class

抽象 类 和构造函数

Abstract classes and constructor

c++

abstract-class

抽象类和构造函数