具有纯虚函数的父类的指针数组和指针数组的对象类型

Posted 2023-02-21

【中文标题】具有纯虚函数的父类的指针数组和指针数组的对象类型

【英文标题】：pointer array of parent class having a pure virtual function and object type of pointer array

【发布时间】：2019-11-27 19:29:46

【问题描述】：

在主函数中，我想创建一个指针数组。对象类型应该每次都改变。 像这样的东西。 shape* a[10]=新矩形； 但我想制作一个 [0] 矩形类型。 a[1] 圆形等。

class shape

    public:
        virtual float boundary_length()=0;
;
class rectangle: public shape

    public:
        float boundary_length()
        
            cout<<"Boundary length of rectangle"<<endl;
            return 2*(length+width);
        
;
class circle: public shape


    public:
        float boundary_length()
        
            return 2*(3.14*radius);
           
;
class triangle: public shape

        float boundary_length()
        
            return (base+perp+hyp);
        
;
int main()

    shape* a=new rectangle;
    return 0;

【参考方案1】：

如果我的理解正确，您需要类似以下内容

#include <iostream>

class shape

    public:
        virtual float boundary_length() const = 0;
        virtual ~shape() = default;
;

class rectangle: public shape

    public:
        rectangle( float length, float width ) : length( length ), width( width )
        
        
        float boundary_length() const override
        
            return 2*(length+width);
        
    protected:
        float length, width;
;

class circle: public shape

    public:
        circle( float radius ) : radius( radius )
        
        
        float boundary_length() const override
        
            return 2*(3.14*radius);
        

    private:
        float radius;
;

//...

int main(void) 

    const size_t N = 10;    
    shape * a[N] =
    
        new rectangle( 10.0f, 10.0f ), new circle( 5.0f )
    ;

    for ( auto s = a; *s != nullptr; ++s )
    
        std::cout << ( *s )->boundary_length() << '\n';
            

    for ( auto s = a; *s != nullptr; ++s )
    
        delete *s;
            

程序输出是

40
31.4