c++继承机制:
代码
#include<iostream>
using namespace std;
class Base
{
private:
int pri_att;
void pri_show()
{
cout<<"Base ::pri_show() is called!"<< endl;
}
protected:
int pro_stt;
void pro_show()
{
cout<<"Base::pro_show() is called!"<<endl;
}
public:
Base()
:pri_att(1);pro_att(2);pub_att(3){}
int pub_att;
void pub_show()
{
cout<<"Base::pub_show() is called !"<<endl;
}
}
class Derived:public Base ／／定义Ａ＿Ｄｅｒｉｖｅｄ以ｐｕｂｌｉｃ继承Ｂａｓｅ，
{ public: ／／
void call_fun() ／／
void show() ／／
}; ／／
| Ｂａｓｅ类别的成员 | Ｂａｓｅ类别的存取权限 | Ｄｅｒｉｖｅｄ类别ｐｕｂｌｉｃ继承后存取权限的等级 |
| ｐｕｂ＿ａｔｔ | ｐｕｂｌｉｃ | ｐｕｂｌｉｃ |
| ｐｒｏ＿ａｔｔ | ｐｒｏｔｅｃｔｅｄ | ｐｒｏｔｅｃｔｅｄ |
| ｐｒｉ＿ａｔｔ | ｐｒｉｖａｔｅ | 隐藏 |
| ｐｕｂ＿ｓｈｏｗ | ｐｕｂｌｉｃ | ｐｕｂｌｉｃ |
| ｐｒｏ＿ｓｈｏｗ | ｐｒｏｔｅｃｔｅｄ | ｐｒｏｔｅｃｔ |
| ｐｒｉ＿ｓｈｏｗ | ｐｔｉｖａｔｅ | 隐藏 |
void Derived::call_fun() ／／
{
cout<<endl;
cout<<"Derived ::call_fun is called"<<endl;
pub_show();
pro_show();
／／ｐｒｉ＿ｓｈｏｗ（）；
}
void Deeived::show()
{
cout<<endl;
cout<<"Derived ::show() is called!"<<endl;
cout<<"Base::pub_att="<<pub_att<<endl;
cout<<"Base::pro_att="<<pro_att<<endl;
／／cout<<"Base::pri_att="<<pri_att<<endl;
}
int main()
{
Derived A_Derived;
cout<<"Accessing Derived's data members"
<<"inherited form Base..."<<endl;
cout<<"Derived::pub_att="<<A_Derived.pub_att<<endl;
／／cout<<"Derived::pro_att="<<A_Derived.pro_att<<endl;
cout<<endl;
cout<<"Call Derived's members funcitons"<<"inherited form Base.."<<endl;
A_Derived.pub_show();
／／A_Derived.pro_show();
／／A_Derived.pri_show();
A_Derived.call_show();
A_Derived.show();
return 0;
}
[root@localhost code]# g++ public_inh.cpp
public_inh.cpp:19: function body for constructor missing
public_inh.cpp:19: invalid data member initialization
public_inh.cpp:19: (use `=' to initialize static data members)
public_inh.cpp:19: ISO C++ forbids declaration of `pro_att' with no type
public_inh.cpp:19: ISO C++ forbids declaration of `pub_att' with no type
public_inh.cpp:19: syntax error before `{' token
public_inh.cpp:19: missing ';' before right brace
public_inh.cpp:20: semicolon missing after declaration of `Base'
public_inh.cpp: In constructor `Base::Base()':
public_inh.cpp:19: parse error before `int'
public_inh.cpp: At global scope:
public_inh.cpp:20: extraneous `int' ignored
public_inh.cpp:20: conflicting types for `Base pub_att'
public_inh.cpp:19: previous declaration as `int pub_att'
public_inh.cpp:25: parse error before `}' token
public_inh.cpp:29: parse error before `void'
public_inh.cpp:30: missing ';' before right brace
public_inh.cpp:38: syntax error before `::' token
public_inh.cpp:41: syntax error before `<<' token
public_inh.cpp:42: syntax error before `<<' token
public_inh.cpp:43: syntax error before `<<' token
public_inh.cpp:44: syntax error before `<<' token
public_inh.cpp: In function `int main()':
public_inh.cpp:53: `class Derived' has no member named `pub_att'
public_inh.cpp:58: no matching function for call to `Derived::pub_show()'
public_inh.cpp:14: `void Base::pro_show()' is protected
public_inh.cpp:59: within this context
public_inh.cpp:8: `void Base::pri_show()' is private
public_inh.cpp:60: within this context
public_inh.cpp:61: no matching function for call to `Derived::call_show()'
public_inh.cpp:62: no matching function for call to `Derived::show()'
根据以上报错，
一一分析排查：
:pri_att(1),pro_att(2),pub_att(3){}
主要还是大部分在细节上，非技术性错误．
经过修改在编译：
public_inh.cpp: In constructor `Base::Base()':
public_inh.cpp:19: class `Base' does not have any field named `pro_att'
public_inh.cpp: In member function `void Derived::show()':
public_inh.cpp:43: `pro_att' undeclared (first use this function)
public_inh.cpp:43: (Each undeclared identifier is reported only once for each
function it appears in.)
public_inh.cpp:6: `int Base::pri_att' is private
public_inh.cpp:44: within this context
public_inh.cpp: In function `int main()':
public_inh.cpp:54: `class Derived' has no member named `pro_att'
public_inh.cpp:14: `void Base::pro_show()' is protected
public_inh.cpp:59: within this context
public_inh.cpp:8: `void Base::pri_show()' is private
public_inh.cpp:60: within this context
public_inh.cpp:61: no matching function for call to `Derived::call_show()'
再修改，编译：
[root@localhost code]# g++ public_inh.cpp
public_inh.cpp: In member function `void Derived::show()':
public_inh.cpp:6: `int Base::pri_att' is private
public_inh.cpp:44: within this context
public_inh.cpp: In function `int main()':
public_inh.cpp:12: `int Base::pro_att' is protected
public_inh.cpp:54: within this context
public_inh.cpp:14: `void Base::pro_show()' is protected
public_inh.cpp:59: within this context
public_inh.cpp:8: `void Base::pri_show()' is private
public_inh.cpp:60: within this context
这就很好证实了在ｐｕｂｌｉｃ继承中ｐｒｉ＿ａｔｔ的不可见性
再次编译
出错情况：
[root@localhost code]# g++ public_inh.cpp
public_inh.cpp: In function `int main()':
public_inh.cpp:12: `int Base::pro_att' is protected
public_inh.cpp:54: within this context
[root@localhost code]# g++ public_inh.cpp
[root@localhost code]# g++ -o public_inh.cpp public_inh.out
g++: public_inh.out: No such file or directory
g++: no input files
但是：
[root@localhost code]# g++ public_inh.cpp -o public_inh.out 成功编译
[root@localhost code]#
结果如下：
[root@localhost code]# g++ public_inh.cpp -o public_inh.out
[root@localhost code]# ./public_inh.out
Accessing Derived's data membersinherited form Base...
Derived::pub_att=3
Call Derived's members funcitonsinherited form Base..
Base::pub_show() is called !
Derived ::call_fun is called
Base::pub_show() is called !
Base::pro_show() is called!
Derived ::show() is called!
Base::pub_att=3
Base::pro_att=2
本程序测试的特点：
| Ｂａｓｅ 类别成员 | Ｂａｓｅ类别存取权限的等级 | Ｄｅｒｉｖｅ类别ｐｕｂｌｉｃ继承后存取权限的等级 | 在类别的外程序可否通过Ｄｅｒｉｖｅｄ类别的对象存取 |
| ｐｕｂ＿ａｔｔ | |||
| ｐｒｏ＿ａｔｔ | |||
| ｐｒｉ＿ａｔｔ | |||
| ｐｕｂ＿ｓｈｏｗ | |||
| ｐｒｏ＿ｓｈｏｗ | |||
代码：
#include<iostream>
#include<cstring>
using namespace std;
class library_object
{
protected:
char name[30];
long index;
public:
void set_data(const char *i_name)
{
strcpy(name,i_name);
index =1;
}
};
class Book :public library_object
{
private:
bool on_shelf;
public :
void show_data()
{
cout<<"name:"<<name;
cout<<"index:"<<index;
if(on_shelf==true)
cout<<"on shelf"<<endl;
else
cout<<"not on shelf "<<endl;
}
};
class Reader :public library_object
{
public :
void show_data()
{
cout<<"name:"<<name;
cout<<"index:"<<index<<endl;
}
};
int main()
{
Reader A_Reader ;
Book A_Book;
A_Reader.set_data("Jorn");
A_Reader.show_data();
A_Book.set_data("the C++ Bible");
A_Book.show-data();
return 0;
}
[root@localhost code]# g++ inheritance.cpp
inheritance.cpp: In function `int main()':
inheritance.cpp:47: `class Book' has no member named `show'
inheritance.cpp:47: `data' undeclared (first use this function)
inheritance.cpp:47: (Each undeclared identifier is reported only once for each
function it appears in.)
显然是一个小错：
[root@localhost code]# g++ inheritance.cpp -o inheritance.out
[root@localhost code]# ./inheritance.out
name:Jornindex:1
name:the C++ Bibleindex:1not on shelf
[root@localhost code]#
程序分析：
ｐｒａｖｉｔｅ继承代码；
#include<iostream>
using namespace std;
class Base
{
private: int pri_att;
void pri_show()
{ cout<<"Base::pri_show() is called!"<<endl;}
protected: int pro_att;
void pro_show()
{ cout<<"Base::pro_show() is called!"<<endl;}
public : int pub_att;
void pub_show()
{ cout<<"Base::pub_show() is called!"<<endl;}
Base()
:pri_att=1;pro_att=1;pub-att=3;
}
class Derived:private Base
{
public :
void call_fun();
void show();
};
void Derived ::call_fun()
{
cout<<endl;
cout<<endl;
cout<<endl;
cout<<endl;
cout<<"Derived ::call_fun is called!"<<endl;
pub_show();
pro_show();
// pri_show();
}
void Derived::show()
{
cout<<endl;
cout<<"Derived ::show() is called "<<endl;
cout<<Derived.pubshow<<endl;
cout<<Derived.proshow<<endl;
cout<<"Base::pub_att="<<pub_att<<endl;
cout<<"Base::pro_att="<<pro_att<<endl;
// cout<<"Base::pri_att="<<pro_att<<endl;
}
int main()
{
return 0;
｝
出错如下:
[root@localhost code]# g++ private_inh.cpp
private_inh.cpp:15: function body for constructor missing
private_inh.cpp:15: ISO C++ forbids declaration of `pro_att' with no type
private_inh.cpp:15: ISO C++ forbids initialization of member `pro_att'
private_inh.cpp:15: making `pro_att' static
private_inh.cpp:15: ISO C++ forbids in-class initialization of non-const static
member `pro_att'
private_inh.cpp:15: declaration of `int Base::pro_att'
private_inh.cpp:8: conflicts with previous declaration `int Base::pro_att'
private_inh.cpp:15: syntax error before `-' token
private_inh.cpp:15: duplicate member `Base::pro_att'
private_inh.cpp:17: semicolon missing after declaration of `Base'
private_inh.cpp: In constructor `Base::Base()':
private_inh.cpp:15: parse error before `:' token
private_inh.cpp: At global scope:
private_inh.cpp:22: multiple types in one declaration
private_inh.cpp: In member function `void Derived::show()':
private_inh.cpp:38: parse error before `.' token
private_inh.cpp:39: parse error before `.' token
private_inh.cpp: At global scope:
private_inh.cpp:50: parse error before `}' token
修改之后;
[root@localhost code]# g++ private_inh.cpp
private_inh.cpp:17: semicolon missing after declaration of `Base'
private_inh.cpp:22: multiple types in one declaration
private_inh.cpp: In member function `void Derived::show()':
private_inh.cpp:38: parse error before `.' token
private_inh.cpp:39: parse error before `.' token
编译出错：
: `Second_Derived Second_Derived::call_fun()' and `void
Second_Derived::call_fun()' cannot be overloaded
private_inh.cpp:53: semicolon missing after declaration of `class
Second_Derived'
private_inh.cpp: In member function `void Second_Derived::show()':
private_inh.cpp:69: parse error before `{' token
private_inh.cpp:74: `A_Dervied' undeclared (first use this function)
private_inh.cpp:74: (Each undeclared identifier is reported only once for each
function it appears in.)
private_inh.cpp:81: `A_Derived' undeclared (first use this function)
private_inh.cpp:87: return-statement with a value, in function declared with a
void return type
[root@localhost code]#