C ++继承/重新定义错误

Question

The Shape Header File

ERROR: Constructor for 'Rectangle' must explicitly initialize the base class 'Shape' which does not have a default constructor

 #ifndef Rectangle_hpp
#define Rectangle_hpp

#include "shape.hpp"

#include <stdio.h>

class Rectangle:public Shape{
    double m_length;
    double m_width;
public:
    Rectangle(double length,double width):Shape("Rectangle"){}
    double getPerimeter();
    double getArea();

};

#endif /* Rectangle_hpp */

The Shape cpp File

ERROR: Redefinition of 'Rectangle'

#include "Rectangle.hpp"

#include "shape.hpp"
#include "Rectangle.hpp"

Rectangle::Rectangle(double length,double width):Shape("Rectangle"){
    m_length = length;
    m_width = width;
}
double Shape::getPerimeter(){
    return 2;
}
double Shape::getArea(){
    return 2;
}

BASE class Header File

#ifndef shape_hpp
#define shape_hpp

#include <stdio.h>

class Shape{
    const char* m_name;
public:
    Shape(const char* name);
    virtual double getPerimeter()=0;
    virtual double getArea()=0;
    char getType();
};

#endif /* shape_hpp */

Base Class cpp file

#include "shape.hpp"

Shape::Shape(const char* name){
    m_name = name;
}

char Shape::getType(){
    return *m_name ;
}

I made another class "Circle" with the same layout as Rectangle and didnt get any errors, these errors are only appearing the the rectangle class.. i am stuck and have no idea why.

Answer 1

In your header file you define the Rectangle constructor with an empty body {} .

In you CPP file you define the Rectangle constructor again. It's complaining about the duplication.

Your header file should only contain the declaration:

Rectangle(double length, double width);

Answer 2

1. ERROR: Constructor for 'Rectangle' must explicitly initialize the base class 'Shape' which does not have a default constructor

this error should not exist and it does not in my machine (GCC 4.9.2)

2. ERROR: Redefinition of 'Rectangle'

In your Rectangle.hpp, you had define the constructor of class Rectangle, you need just to declare it

Rectangle(double length,double width)