Facade-----结构型设计模式之一

Facade为子系统的一组接口提供一个一致的界面,比如对数据库的访问,当从一种数据换为另外一种的时候,接口不变,因此客户端不变,减少了耦合度.

列举:

#include                // MFC DAO database classes.
class DB
{
       static CDaoDatabase s_db;
public:
       static void Init()
       {
              try
              {
                     s_db.Open(_T("*.mdb"),FALSE,FALSE,";pwd=1");
              }catch(CDaoException *e)
              {
                     AfxMessageBox(e->m_pErrorInfo->m_strDescription);
                     return;
              }
       }
       void Store(int iid,int icount)
       {
              try
              {
                     s_db.Excute(BuildInsertionStatement(iid,icount));
              }catch(CDaoException * e)
              {
                     AfxMessageBox(e->m_pErrorInfo->m_strDescription);
                     return;
              }
       }
private:
        CString BuildInsertionStatement(int iid,int icount)
       {
              CString str;
              str.Format ("Insert inter Products value ('%d','% d'),pd.ID,pd.Count");
              return str;
       }
}

//client

void main()

{

      DB.Init();

      DB.Store(1,5);

}

注:以上是实现插入access数据库的例子,改变数据库为sql server的时候,改变DB中的s_db和Init()相关的函数和变量,不改变client中的代码.减少了耦合度.