目前我正在开发一个处于初始阶段的设计，下面是我迄今为止做过的一些功课，但它似乎没有问题，而且我一直面临着一些问题。从下面的代码可以清楚地看出，设备工厂已经用于设备对象和库对象的创建目的。 现在的工作是从工厂获取设备对象后，将调用connect函数，这将确保连接成功完成，现在需要使用任何相关的解析器（XML，JSON或其他支持的解析器）来获取数据。现在这里的任务（设备和库的选择）都是单独完成的，所以现在的工作是我需要在选定的对象上强加选定的库，并且对于相同的赋值操作符已经在Device类中重载但是我收到错误＆＃34;不能转换＆＃39;图书馆*＆＃39;到设备*＆＃39;在任务＆＃34;将库对象分配给设备对象时。除此之外，我还需要使用Library类作为抽象类，这在当前实现中是不可能的。
#include<iostream>
#include<string.h>
using namespace std;
class Library
{
public:
virtual void lib_func();
virtual ~Library(){}
};
class JSON : public Library
{
public:
void lib_func()
{
cout<<"connect through USB"<<endl;
}
};
class JXML : public Library
{
public:
void lib_func()
{
cout<<"Connect through TCP"<<endl;
}
};
class XML : public Library
{
public:
void lib_func()
{
cout<<" connect through BT"<<endl;
}
};
class Device
{
public:
virtual void connect()=0;
const Device& operator =(const Device& obj);
virtual ~Device(){}
private:
Library * obj;
};
const Device& Device:: operator =(const Device& rhs)
{
Library *objorig=obj;
obj=new Library(*rhs.obj);
delete objorig;
return *this;
}
class D1: public Device
{
public:
void connect()
{
cout<<" connect through USB"<<endl;
}
};
class D2 : public Device
{
public:
void connect()
{
cout<<"Connect through TCP"<<endl;
}
};
class D3 : public Device
{
public:
void connect()
{
cout<<" connect through BT"<<endl;
}
};
class Devicefactory
{
public:
virtual Device* create_instance(const char* type)=0;
virtual Library* populate_library(const char* type)=0;
};
class factory : public Devicefactory
{
public:
Device* create_instance(const char* type)
{
if(!strcmp(type,"D1"))
{
return new D1();
}
else if(!strcmp(type,"D2"))
{
return new D2();
}
else if(!strcmp(type,"D3"))
{
return new D3();
}
return NULL;
}
Library* populate_library(const char* type)
{
if(!strcmp(type,"XML"))
{
return new XML();
}
else if(!strcmp(type,"JSON"))
{
return new JSON();
}
else if(!strcmp(type,"JXML"))
{
return new JXML();
}
return NULL;
}
};
int main()
{
Devicefactory *obj=new factory;
Device * object = obj->create_instance("D3");
Library *object1 = obj->populate_library("JSON");
object->connect();
object=object1;
object->lib_func();
delete object;
delete obj;
return 1;
}
答案 0 :(得分：0)
我可能遗漏了一些内容，但在我看来，您只需要向setLibrary添加Device成员函数：
void setLibrary(Library* library) {
obj = library;
}
然后在你的main函数中使用它：
Device* object = obj->create_instance("D3");
Library* object1 = obj->populate_library("JSON");
object.setLibrary(object1);
我假设设备不应该拥有该库，而您只是想将该库与设备相关联。
无需编写赋值运算符。
您可能打算在lib_func中提取Library摘要：
virtual void lib_func() = 0;
偏离主题：我建议您从工厂返回std::unique_ptr而不是原始指针，这样您就不必记得拨打delete（您忘了删除{ {1}}）。没有理由使用Library分配工厂，你可以在堆栈上创建它。
答案 1 :(得分：0)
使用私有继承来实现相同的功能，这样就可以覆盖Device类中的虚函数lib_info并实现相同的功能。除了这种方法之外，您的Library类将是抽象的.Below是您需要使用的方法来避免任何赋值错误。通常，私有继承用于覆盖组合不可能的虚函数。 第1步：覆盖Device类中的lib_func。
class Device : private Library
{
public:
virtual void connect()=0;
void lib_func();
virtual ~Device(){}
};
第2步： 下面是重写函数的实现
void Device :: lib_func（） {
Devicefactory * obj =新工厂;
Library *object1=obj->populate_library("JSON");
object1->lib_func();
}
第3步： 现在你只需要在驱动程序函数中使用Device对象，这就是类 抽象。
int main()
{
Devicefactory *obj=new factory;
Device * object=obj->create_instance("D3");
object->connect();
object->lib_func();
delete object;
delete obj;
return 1;
}
答案 2 :(得分：0)
Below is the approach which is implemented through without assignment operator and private inheritance.
#include<fstream>
#include<iostream>
#include<string.h>
#include<memory>
#define RESULT_ERROR 0
#define RESULT_SUCCESS 1
using namespace std;
class Library
{
public:
virtual void lib_func(fstream &obj)=0;
virtual ~Library(){}
};
class JSON : public Library
{
public:
void lib_func(fstream &obj)
{
cout<<"using json to fetch the object"<<endl;
}
};
class JXML : public Library
{
public:
void lib_func(fstream &obj)
{
cout<<"using JXML to fetch the object"<<endl;
}
};
class XML : public Library
{
public:
void lib_func(fstream &obj)
{
cout<<"use XML to fetch the data"<<endl;
}
};
class Device
{
public:
Device( Library *lib=NULL) : lib(lib){}
virtual void connect()=0;
int16_t impose_library(fstream &obj);
virtual ~ Device(){}
protected:
Library *lib;
};
class D1: public Device
{
public:
D1():Device(lib)
{
}
void connect()
{
cout<<" connect through USB"<<endl;
}
};
class D2 : public Device
{
public:
D2():Device(lib)
{
}
void connect()
{
cout<<"Connect through TCP"<<endl;
}
};
class D3 : public Device
{
public:
D3():Device(lib)
{
}
void connect()
{
cout<<" connect through BT"<<endl;
}
};
class Devicefactory
{
public:
virtual Device* create_instance(const char* type)=0;
virtual Library* populate_library(const char* type)=0;
};
class factory : public Devicefactory
{
public:
Device* create_instance(const char* type)
{
if(!strcmp(type,"D1"))
{
return new D1();
}
else if(!strcmp(type,"D2"))
{
return new D2();
}
else if(!strcmp(type,"D3"))
{
return new D3();
}
return NULL;
}
Library* populate_library(const char* type)
{
if(!strcmp(type,"XML"))
{
return new XML();
}
else if(!strcmp(type,"JSON"))
{
return new JSON();
}
else if(!strcmp(type,"JXML"))
{
return new JXML();
}
return NULL;
}
};
int16_t Device :: impose_library(fstream &fconfig)
{
std::unique_ptr <Devicefactory> obj (new factory);
std::unique_ptr<Library> object1 (obj->populate_library("JSON"));
if(object1!=NULL)
{
object1->lib_func(fconfig);
return RESULT_SUCCESS;
}
else
{
return RESULT_ERROR;
}
}
int main()
{
int16_t result;
fstream fconfig ;
std::unique_ptr<Devicefactory> obj (new factory);
std::unique_ptr<Device> object(obj->create_instance("D3"));
object->connect();
result=object->impose_library(fconfig);
if(result==RESULT_ERROR)
{
cout<<"NULL object"<<endl;
}
return 1;
}