(原創) 試試看你手上對付問題有幾種武器!! (C/C++) (.NET) (C#)
GoF Design Pattern p.22說，物件導向對付問題有三種方法：1.物件繼承，2.物件多型，3.物件泛型，若加上程序導向，我們手中最少有四種武器對付問題，你會哪幾種呢?
一個簡單的需求，我們要抓資料，但資料同時可能在SQL Server，也可能在Oracle，將來還有可能有其他Database Server，所以我們必須最少實做兩種方式。
執行結果
Get Data from SQL ServerGet Data from Oracle
第一種，程序導向(Procedure Oriented)
C++
1
/*
2
(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_Procedure.cpp
5Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++
6Description : Demo how to solve problem by procedure
7Release : 04/07/2007 1.0
8
*/
9#include <iostream>
10
11using namespace std;
12
13void getDataFromSQL() {
14 cout << "Get Data from SQL Server" << endl;
15}
16
17void getDataFromOracle() {
18 cout << "Get Data from Oracle" << endl;
19}
20
21int main() {
22 getDataFromSQL();
23 getDataFromOracle();
24}
/* 
2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_Procedure.cpp5
Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++6
Description : Demo how to solve problem by procedure 7
Release : 04/07/2007 1.08
*/9
#include <iostream>10
11
using namespace std;12
13
void getDataFromSQL() {
14
cout << "Get Data from SQL Server" << endl; 15
}16
17
void getDataFromOracle() {18
cout << "Get Data from Oracle" << endl;19
}20
21
int main() {22
getDataFromSQL();23
getDataFromOracle();24
}
C#
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_Procedure.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to solve problem by procedure
7Release : 04/07/2007 1.0
8*/
9using System;
10
11class main {
12
public static void getDataFromSQL() {
13 Console.WriteLine("Get Data from SQL Server");
14
}
15
16 public static void getDataFromOracle() {
17 Console.WriteLine("Get Data from Oracle");
18 }
19
20 public static void Main() {
21 getDataFromSQL();
22 getDataFromOracle();
23 }
24}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_Procedure.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to solve problem by procedure 7
Release : 04/07/2007 1.08
*/9
using System;10
11
class main {12
public static void getDataFromSQL() {
13
Console.WriteLine("Get Data from SQL Server");14
}15
16
public static void getDataFromOracle() {17
Console.WriteLine("Get Data from Oracle");18
}19
20
public static void Main() {21
getDataFromSQL();22
getDataFromOracle();23
}24
}
第二種，物件繼承(Object Inheritance)
C++
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_OO_Inheritance.cpp
5Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++
6Description : Demo how to solve problem by Object Inheritance
7Release : 04/07/2007 1.0
8*/
9#include <iostream>
10
11using namespace std;
12
13class DBManager {
14public:
15 void getData() {
16 this->getDataFromDB();
17 }
18
19protected:
20 virtual void getDataFromDB() {}
21};
22
23class SQLDBManager : public DBManager {
24protected:
25 void getDataFromDB() {
26 cout << "Get Data from SQL Server" << endl;
27 }
28};
29
30class OracleDBManager : public DBManager {
31protected:
32 void getDataFromDB() {
33 cout << "Get Data from Oracle" << endl;
34 }
35};
36
37int main() {
38 DBManager* theDBManager = &SQLDBManager();
39 theDBManager->getData();
40
41 theDBManager = &OracleDBManager();
42 theDBManager->getData();
43}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_OO_Inheritance.cpp5
Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++6
Description : Demo how to solve problem by Object Inheritance7
Release : 04/07/2007 1.08
*/9
#include <iostream>10
11
using namespace std;12
13
class DBManager {14
public:15
void getData() {16
this->getDataFromDB();17
}18
19
protected:20
virtual void getDataFromDB() {}21
};22
23
class SQLDBManager : public DBManager {24
protected:25
void getDataFromDB() {26
cout << "Get Data from SQL Server" << endl; 27
}28
};29
30
class OracleDBManager : public DBManager {31
protected:32
void getDataFromDB() {33
cout << "Get Data from Oracle" << endl;34
}35
};36
37
int main() {38
DBManager* theDBManager = &SQLDBManager();39
theDBManager->getData();40
41
theDBManager = &OracleDBManager();42
theDBManager->getData();43
}
C#
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_OO_Inheritance.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to solve problem by Object Inheritance
7Release : 04/07/2007 1.0
8*/
9using System;
10
11class DBManager {
12 public void getData() {
13 this.getDataFromDB();
14 }
15
16 protected virtual void getDataFromDB() {}
17}
18
19class SQLDBManager : DBManager {
20 protected override void getDataFromDB() {
21 Console.WriteLine("Get Data from SQL Server");
22 }
23}
24
25class OracleDBManager : DBManager {
26 protected override void getDataFromDB() {
27 Console.WriteLine("Get Data from Oracle");
28 }
29}
30
31class main {
32 public static void Main() {
33 DBManager theDBManager = new SQLDBManager();
34 theDBManager.getData();
35
36 theDBManager = new OracleDBManager();
37 theDBManager.getData();
38 }
39}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_OO_Inheritance.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to solve problem by Object Inheritance7
Release : 04/07/2007 1.08
*/9
using System;10
11
class DBManager {12
public void getData() {13
this.getDataFromDB();14
}15
16
protected virtual void getDataFromDB() {}17
}18
19
class SQLDBManager : DBManager {20
protected override void getDataFromDB() {21
Console.WriteLine("Get Data from SQL Server");22
}23
}24
25
class OracleDBManager : DBManager {26
protected override void getDataFromDB() {27
Console.WriteLine("Get Data from Oracle");28
}29
}30
31
class main {32
public static void Main() {33
DBManager theDBManager = new SQLDBManager();34
theDBManager.getData();35
36
theDBManager = new OracleDBManager();37
theDBManager.getData();38
}39
}
第三種，物件多型(Object Polymorphism)
C++
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_OO_Polymorphism.cpp
5Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++
6Description : Demo how to solve problem by Object Polymorphism
7Release : 04/07/2007 1.0
8*/
9#include <iostream>
10
11using namespace std;
12
13class IDBServer {
14public:
15 virtual void getDataFromDB() = 0;
16};
17
18class DBManager {
19private:
20 IDBServer* dBServer;
21
22public:
23 DBManager() {}
24 DBManager(IDBServer& dBServer) : dBServer(&dBServer) {}
25
26public:
27 void getData() {
28 this->dBServer->getDataFromDB();
29 }
30};
31
32class SQLServer : public IDBServer {
33public:
34 void getDataFromDB() {
35 cout << "Get Data from SQL Server" << endl;
36 }
37};
38
39class Oracle : public IDBServer {
40public:
41 void getDataFromDB() {
42 cout << "Get Data from Oracle" << endl;
43 }
44};
45
46int main() {
47 DBManager& theDBManager = DBManager(SQLServer());
48 theDBManager.getData();
49
50 theDBManager = DBManager(Oracle());
51 theDBManager.getData();
52}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_OO_Polymorphism.cpp5
Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++6
Description : Demo how to solve problem by Object Polymorphism7
Release : 04/07/2007 1.08
*/9
#include <iostream>10
11
using namespace std;12
13
class IDBServer {14
public:15
virtual void getDataFromDB() = 0;16
};17
18
class DBManager {19
private:20
IDBServer* dBServer;21
22
public:23
DBManager() {}24
DBManager(IDBServer& dBServer) : dBServer(&dBServer) {}25
26
public:27
void getData() {28
this->dBServer->getDataFromDB();29
}30
};31
32
class SQLServer : public IDBServer {33
public:34
void getDataFromDB() {35
cout << "Get Data from SQL Server" << endl; 36
}37
};38
39
class Oracle : public IDBServer {40
public:41
void getDataFromDB() {42
cout << "Get Data from Oracle" << endl;43
}44
};45
46
int main() {47
DBManager& theDBManager = DBManager(SQLServer());48
theDBManager.getData();49
50
theDBManager = DBManager(Oracle());51
theDBManager.getData();52
}
C#
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_OO_Polymorphism.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to solve problem by Object Polymorphism
7Release : 04/07/2007 1.0
8*/
9using System;
10
11interface IDBServer {
12 void getDataFromDB();
13}
14
15class DBManager {
16 private IDBServer dBServer;
17
18 public DBManager() {}
19 public DBManager(IDBServer dBServer) {
20 this.dBServer = dBServer;
21 }
22
23 public void getData() {
24 this.dBServer.getDataFromDB();
25 }
26}
27
28class SQLServer : IDBServer {
29 public void getDataFromDB() {
30 Console.WriteLine("Get Data from SQL Server");
31 }
32}
33
34class Oracle : IDBServer {
35 public void getDataFromDB() {
36 Console.WriteLine("Get Data from Oracle");
37 }
38}
39
40class main {
41 public static void Main() {
42 DBManager theDBManager = new DBManager(new SQLServer());
43 theDBManager.getData();
44
45 theDBManager = new DBManager(new Oracle());
46 theDBManager.getData();
47 }
48}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_OO_Polymorphism.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to solve problem by Object Polymorphism7
Release : 04/07/2007 1.08
*/9
using System;10
11
interface IDBServer {12
void getDataFromDB();13
}14
15
class DBManager {16
private IDBServer dBServer;17
18
public DBManager() {}19
public DBManager(IDBServer dBServer) {20
this.dBServer = dBServer;21
}22
23
public void getData() {24
this.dBServer.getDataFromDB();25
}26
}27
28
class SQLServer : IDBServer {29
public void getDataFromDB() {30
Console.WriteLine("Get Data from SQL Server"); 31
}32
}33
34
class Oracle : IDBServer {35
public void getDataFromDB() {36
Console.WriteLine("Get Data from Oracle");37
}38
}39
40
class main {41
public static void Main() {42
DBManager theDBManager = new DBManager(new SQLServer());43
theDBManager.getData();44
45
theDBManager = new DBManager(new Oracle());46
theDBManager.getData();47
}48
}
第四種，物件泛型 (Object Generic)
C++
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_GP_template.cpp
5Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++
6Description : Demo how to solve problem by template
7Release : 04/07/2007 1.0
8*/
9#include <iostream>
10
11using namespace std;
12
13template <typename T>
14class DBManager {
15private:
16 T* dBServer;
17
18public:
19 void getData() {
20 this->dBServer->getDataFromDB();
21 }
22};
23
24class SQLServer {
25public:
26 void getDataFromDB() {
27 cout << "Get Data from SQL Server" << endl;
28 }
29};
30
31class Oracle {
32public:
33 void getDataFromDB() {
34 cout << "Get Data from Oracle" << endl;
35 }
36};
37
38int main() {
39 DBManager<SQLServer> theDBManager1;
40 theDBManager1.getData();
41
42 DBManager<Oracle> theDBManager2;
43 theDBManager2.getData();
44}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_GP_template.cpp5
Compiler : Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++6
Description : Demo how to solve problem by template7
Release : 04/07/2007 1.08
*/9
#include <iostream>10
11
using namespace std;12
13
template <typename T>14
class DBManager {15
private:16
T* dBServer; 17
18
public:19
void getData() {20
this->dBServer->getDataFromDB();21
}22
};23
24
class SQLServer {25
public:26
void getDataFromDB() {27
cout << "Get Data from SQL Server" << endl; 28
}29
};30
31
class Oracle {32
public:33
void getDataFromDB() {34
cout << "Get Data from Oracle" << endl;35
}36
};37
38
int main() {39
DBManager<SQLServer> theDBManager1;40
theDBManager1.getData();41
42
DBManager<Oracle> theDBManager2;43
theDBManager2.getData();44
}
C#
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : SQLOracle_GP_Generic.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to solve problem by Generic
7Release : 04/07/2007 1.0
8*/
9using System;
10interface IDBServer {
11 void getDataFromDB();
12}
13
14class DBManager<T> where T : IDBServer, new(){
15 private T dBServer;
16
17 public DBManager() {
18 this.dBServer = new T();
19 }
20
21 public void getData() {
22 this.dBServer.getDataFromDB();
23 }
24}
25
26class SQLServer : IDBServer{
27 public void getDataFromDB() {
28 Console.WriteLine("Get Data from SQL Server");
29 }
30}
31
32class Oracle : IDBServer{
33 public void getDataFromDB() {
34 Console.WriteLine("Get Data from Oracle");
35 }
36}
37
38class main {
39 public static void Main() {
40 DBManager<SQLServer> theDBManager1 = new DBManager<SQLServer>();
41 theDBManager1.getData();
42
43 DBManager<Oracle> theDBManager2 = new DBManager<Oracle>();
44 theDBManager2.getData();
45 }
46}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : SQLOracle_GP_Generic.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to solve problem by Generic7
Release : 04/07/2007 1.08
*/9
using System;10
interface IDBServer {11
void getDataFromDB();12
}13
14
class DBManager<T> where T : IDBServer, new(){15
private T dBServer; 16
17
public DBManager() {18
this.dBServer = new T();19
}20
21
public void getData() {22
this.dBServer.getDataFromDB();23
}24
}25
26
class SQLServer : IDBServer{27
public void getDataFromDB() {28
Console.WriteLine("Get Data from SQL Server");29
}30
}31
32
class Oracle : IDBServer{33
public void getDataFromDB() {34
Console.WriteLine("Get Data from Oracle");35
}36
}37
38
class main {39
public static void Main() {40
DBManager<SQLServer> theDBManager1 = new DBManager<SQLServer>();41
theDBManager1.getData();42
43
DBManager<Oracle> theDBManager2 = new DBManager<Oracle>();44
theDBManager2.getData();45
}46
}
Conclusion
同一種問題，用不同方式實做，各有各的優缺點，不過通常以彈性跟好維護來說，泛型 > 多型 >> 繼承 >> 程序，你手上有多少武器呢?
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