Question

基本上我有两个抽象类IVisitor和IVisitable，Product和Order正在扩展IVisitable而报告正在扩展IVisitor，所以Report可以访问Order和Product并计算订单或产品的数量。

我得到一些我无法解决的错误，例如＆＃34;函数不带一个参数＆＃34;当显然，未知标识符等。

以下是代码：

IVisitable.h

#pragma once
#include"IVisitor.h"

class IVisitable{
public:
    virtual void accept(IVisitor *v)=0;
};

IVisitor.h

#pragma once
#include"Product.h"
#include"Order.h"

class IVisitor{
public:
    virtual void visit(Order*)=0;
    virtual void visit(Product*)=0;
};

Order.h

#pragma once
#include<string>
using namespace std;
#include<vector>
#include"Product.h"


class Order : public IVisitable{
public:
    vector<Product> list;

    void accept(IVisitor *v){
        v->visit(this);

        for(int i=0; i<list.size(); i++)
            list[i].accept(v);

    }

};

Product.h

#pragma once
#include<string>
using namespace std;
#include"IVisitable.h"

class Product : public IVisitable{
public:
    string name;
    Product(string i){name = i;}
    Product(){}

    void accept(IVisitor *v){
        v->visit(this);
    }

};

Report.h

#pragma once
#include"IVisitor.h"

class Report : public IVisitor{

public:
    int numProduct;
    int numOrders;

    Report(){
        numProduct = numOrders = 0;
    }

    void visit(Order*){
        numOrders++;
    }

    void visit(Product*){
        numProduct++;
    }

};

Source.cpp

#include<iostream>
#include"Order.h"
#include"Report.h"

using namespace std;

void main(){
    Product p1("eggs");
    Product p2("meat");
    Product p3("milk");

    Order ord1; 
    ord1.list.push_back(p1); 
    ord1.list.push_back(p2);
    ord1.list.push_back(p3);

    Report *report = new Report;

    ord1.accept(report);

    cout<<report->numProduct<<endl;
}

错误：

1>ivisitor.h(7): error C2061: syntax error : identifier 'Order'
1>ivisitor.h(8): error C2061: syntax error : identifier 'Product'
1>ivisitor.h(8): error C2535: 'void IVisitor::visit(void)' : member function already defined or declared
1>ivisitor.h(7) : see declaration of 'IVisitor::visit'
1>product.h(13): error C2660: 'IVisitor::visit' : function does not take 1 arguments
1>order.h(13): error C2660: 'IVisitor::visit' : function does not take 1 arguments
1>order.h(15): warning C4018: '<' : signed/unsigned mismatch
1>source.cpp(17): error C2259: 'Report' : cannot instantiate abstract class
1>          due to following members:
1>          'void IVisitor::visit(void)' : is abstract

Answer 1

头文件之间有一个引用周期。要解决问题，请不要使用

SELECT id,min((arr ->> 2)::numeric) AS custom_value 
FROM ( 
   SELECT id, jdoc
   FROM table, 
        jsonb_each(column1) d (key, jdoc)
   ) sub,
     jsonb_each(jdoc) doc (key, arr) 
group by 1

但请使用

#include "..."

在c ++

1 个答案: