似乎无法使用迭代器在 for 循环中打印 list<VERTEX>vertices？ C++

Question

我遇到一个问题，我无法打印列表 'vertex' 顶点中的坐标集。解释一下，'Vertex' 是一个 class，它基本上包含构成顶点的两个坐标（形状的两条线相交处）。问题出在第二个 for 循环中，该循环旨在打印出列表中的坐标。任何人都可以帮助我尝试打印出来吗？我尝试了很多方法，到目前为止，错误总是给我带来问题。代码如下，感谢帮助！

INT 主

int main(){
//obj
Console con;
RandomNumber rand;
Vertex vertex;

//Declarations
list<Vertex>vertices; 
//list<Vertex>::iterator ii;


//set Vertex coords and push into list
for (int i = 0; i <= 8;  i++){
vertices.push_back(Vertex(rand.random(0, 10), rand.random(0, 10)));
}

//iterate through the list outputting a char at each vertex (coords)
for (list<Vertex>::iterator ii = vertices.begin(); ii != vertices.end(); ii++){
    cout << vertices[ii];
}


system("pause");

}

顶点CLASS

#pragma once
class Vertex
{
    int x;
    int y;
public:
    Vertex(int x = 10, int y = 10);
    ~Vertex();
    int getX() const;
    int getY() const;
    void setX(unsigned x);
    void setY(unsigned y);
    bool operator== (const Vertex &p2) const;
};

    #include "Vertex.h"
Vertex::Vertex(int x, int y)
{
    this->x = x;
    this->y = y;
}
Vertex::~Vertex(){}
int Vertex::getX() const {
    return x;
}
int Vertex::getY() const {
    return y;
}
void Vertex::setX(unsigned x) {
    this->x = x;
}
void Vertex::setY(unsigned y) {
    this->y = y;
}
bool Vertex::operator== (const Vertex &point) const {
    return (this->x == point.getX()) && (this->y == point.getY());
}

Answer 1

//iterate through the list outputting a char at each vertex (coords)
for (list<Vertex>::iterator ii = vertices.begin(); ii != vertices.end(); ii++){
    cout << vertices[ii];
}

这本质上是错误的。您需要将迭代器当作指向列表中第 ii 个对象的指针来使用。

for (list<Vertex>::iterator ii = vertices.begin(); ii != vertices.end(); ii++){
    cout << ii->getX() << ',' << ii->getY(); 
    // if you have an overload for 'operator <<(std::ostream&, Vertex)' you can also do 
    cout << *ii 
}

Answer 2

<< 运算符不适用于自定义类型。您需要指定 << 运算符在遇到您的 Vertex class 时的行为方式。

您需要生成一个能够理解您的顶点的签名 class。取以下函数：

std::ostream& operator<<(std::ostream &os, const Vertex &vertex) {
    os << "Node: [" << vertex.getX() << ", " << vertex.getY() << "]";
    return os;
}

这将允许您使用您编写的代码。

Answer 3

需要给你加一个功能class:

声明：

friend std::ostream& operator <<(std::ostream &os,const Vertex &obj);

和实施：

std::ostream& operator<<( std::ostream &os,const Vertex &obj )
{
    os << << obj.getX() << ',' << obj.getY();
    return os;
}

这将声明 << 运算符的重载，如所见 here.

您还必须将迭代更改为：

for (list<Vertex>::iterator ii = vertices.begin(); ii != vertices.end(); ii++){
    cout << *ii;
}

似乎无法使用迭代器在 for 循环中打印 list<VERTEX>vertices？ C++

Cant seem to print list<VERTEX>vertices within a for loop using an iterator? C++

c++

iterator

for-loop

variable-assignment