Question

我有头文件

#ifndef CATEGORY_H
#define CATEGORY_H

#include <functional>
#include <string>
#include <vector>

class Category
{
    private:
        std::string nameCategory;
        std::vector<Rule> setOfRules;
    protected:
    public:
        Category();
        Category(std::string nameCategory);
        void setIndexBankAccountEntry(unsigned int iBankAccountEntry);
};

class Rule : public Category
{
    private:
        std::function<void(int)> rule;
    protected:
    public:
        Rule();
        Rule(std::function<void(int)> rule);
};
#endif

其中命令std::vector<Rule> setOfRules;给出了Rule尚未声明的错误。

切换两个类的声明顺序给出了

#ifndef CATEGORY_H
#define CATEGORY_H

#include <functional>
#include <string>
#include <vector>

class Rule : public Category
{
    private:
        std::function<void(int)> rule;
    protected:
    public:
        Rule();
        Rule(std::function<void(int)> rule);
};

class Category
{
    private:
        std::string nameCategory;
        std::vector<Rule> setOfRules;
    protected:
    public:
        Category();
        Category(std::string nameCategory);
        void setIndexBankAccountEntry(unsigned int iBankAccountEntry);
};
#endif

然后我收到expected class-name before ‘{’ token行class Rule : public Category的错误。

我该如何解决这个问题？

Answer 1

您可以使用类Rule的前向声明（基于第一个示例）。

class Rule;
class Category
{
    private:
        std::string nameCategory;
        std::vector<Rule> setOfRules;
    protected:
    public:
        Category();
        Category(std::string nameCategory);
        void setIndexBankAccountEntry(unsigned int iBankAccountEntry);
};
// class Rule definition here

检查here

Answer 2

您可以转发声明类规则：

#ifndef CATEGORY_H
#define CATEGORY_H

#include <functional>
#include <string>
#include <vector>

class Rule; // <-- here

class Category
{
    private:
        std::string nameCategory;
        std::vector<Rule> setOfRules;
    protected:
    public:
        Category();
        Category(std::string nameCategory);
        void setIndexBankAccountEntry(unsigned int iBankAccountEntry);
};

class Rule : public Category
{
    private:
        std::function<void(int)> rule;
    protected:
    public:
        Rule();
        Rule(std::function<void(int)> rule);
};
#endif

在基类中使用派生类，而派生类在基类之后声明

2 个答案: