Question

我有一个代码，我正在绘制不同的Shape，现在可以优先选择哪一个首先绘制方形，矩形和三角形。我已经覆盖了“＆lt;” （少于基类Shape的运算符。我对绘图的偏好按照在typeOrderTable中提到的递增顺序。因此三角形将在Square之前绘制但在编译时我得到错误错误：'class std :: vector'没有名为'的成员'排序'。

#include <iostream>
#include <vector>
#include <typeinfo>
#include <string.h>
using namespace std;


class Shape 
{ 
    public: 
    virtual void Draw() const = 0; 
    virtual bool Precedes(const Shape&) const ;
    bool operator<(const Shape& s) 
    {
        return Precedes(s);
    }
    private:    
    static char* typeOrderTable[];
};

char* Shape::typeOrderTable[] = {"Rectangle","Square","Triangle",0 };

bool Shape::Precedes(const Shape& s) const 
{
    const char* thisType = typeid(*this).name();    
    const char* argType = typeid(s).name();    
    bool done = false;    int thisOrd = -1;    
    int argOrd = -1;    
    for (int i=0; !done; i++)    
    {        
        const char* tableEntry = typeOrderTable[i];
        if (tableEntry != 0)        
        {            
            if (strcmp(tableEntry, thisType) == 0)                
            thisOrd = i;            
            if (strcmp(tableEntry, argType) == 0)                
            argOrd = i;
            if ((argOrd > 0) && (thisOrd > 0))                
            done = true;        

        }        
        else // table entry == 0            
        done = true;    
    }    
    return thisOrd < argOrd; 
}

class Square : public Shape 
{ 
    public: 
    virtual void Draw() const 
    { 
        std::cout << "Inside Draw of Square \n" ; 

    } 
};

class Rectangle : public Shape 
{ 
    public: 
    virtual void Draw() const 
    { 
        std::cout << "Inside Draw of Rectangle \n" ; 

    } 
};

class Triangle : public Shape 
{ 
    public: 
    virtual void Draw() const 
    { 
        std::cout << "Inside Draw of Triangle \n" ; 

    } 
};

void DrawAllShapes(std::vector<Shape*>& list) 
{        
    std::vector<Shape*> orderedList = list;
    orderedList.sort();    
    std::vector<Shape*>::iterator it =orderedList.begin();
    for (;it!=orderedList.end(); ++it)
    (*it)->Draw(); 
}

int main() 
{
std::vector<Shape*> vec;
vec.push_back(new Triangle);
vec.push_back(new Square);
vec.push_back(new Rectangle);
vec.push_back(new Square);
DrawAllShapes(vec);
return 0;
}

Answer 1

没有std::vector<...>::sort。相反，您需要使用std::sort：

std::sort(orderedList.begin(), orderedList.end());

然而，这会尝试比较std::vector<Shape*>中的指针（提示：如果可能的话，重构这个）。相反，您需要传递一个自定义比较器来取消引用指针：

std::sort(
    orderedList.begin(),
    orderedList.end(),
    [](Shape *a, Shape *b) { return *a < *b; }
);

错误：'class std :: vector <shape *>'没有名为'sort'的成员

1 个答案: