[C#]橋接模式(Bridge)
目的
為了解決一個介面已經被多個類別給實作，這時候如果我們需要再為此介面新增方法的時候，就會面臨到多支類別都要擴充此方法，就會造成擴充不易，甚至有些可能不需要此方法，這時候就可以多加一個新的介面，然後把原本的介面當成屬性加在新的介面裡面，然後直接呼叫新介面就也會有擁有原本想擴充介面的屬性，也同時擁有新介面的方法或屬性。
情境模擬
在實務上很多都是會定義service對應到某個table的名稱，比如說我們有一個table名為account，那大概就會有相對應的AccountDao和AccountService，那以Service來說我們可能就會擁有了IAccountService，GoogleAccountService和FaceBookAccountService，底下則是程式碼示例
IAccountService
public interface IAccountService
{
string GetAll();
void ModifyPwd();
string Login();
bool IsLogin();
void Remove();
}
類別實作部份
public class FaceBookAccountService : IAccountService
{
public string GetAll()
{
return "Get All FB Account";
}
public bool IsLogin()
{
return true;
}
public string Login()
{
return "Anson is login";
}
public void ModifyPwd()
{
Console.WriteLine("Modify success of FB account");
}
public void Remove()
{
Console.WriteLine("Remove success of FB account");
}
}
public class GoogleAccountService : IAccountService
{
public string GetAll()
{
return "Get All Google Account";
}
public bool IsLogin()
{
return true;
}
public string Login()
{
return "Anson is login";
}
public void ModifyPwd()
{
Console.WriteLine("Modify success of google account");
}
public void Remove()
{
Console.WriteLine("Remove success of google account");
}
}
呼叫端
static void Main(string[] args)
{
IAccountService _service = new GoogleAccountService();
Console.Write(_service.GetAll());
Console.ReadKey();
}
結果
Get All Google Account
可以想像如果有三支或四支共同實做了此介面，那我們介面如果要加一個方法，四支類別都得異動，新增了方法不打緊，就怕根本不需要會造成違反里氏替換原則(不要欺騙實做端，有得呼叫就一定得實做)，那接下來就來看一下橋接模式後的程式碼會長什麼樣子呢，假設我們介面新增了一個TransferAccount的方法，目的是為了要sso轉移去另一個平台。
ISsoService
public interface ISsoService
{
IAccountService AccountService { get; set; }
void TransferAccount();
}
SsoService
public class SsoService : ISsoService
{
IAccountService _accountService = new GoogleAccountService(); //預設會是google的帳號
public IAccountService AccountService //提供屬性讓外面可以替換
{
get
{
return _accountService;
}
set
{
_accountService = value;
}
}
public void TransferAccount()
{
Console.WriteLine("Success of transfer to another web site");
}
}
呼叫端
static void Main(string[] args)
{
ISsoService service = new SsoService();
Console.WriteLine(service.AccountService.GetAll());
service.TransferAccount();
service.AccountService = new FaceBookAccountService();
Console.WriteLine(service.AccountService.GetAll());
Console.ReadKey();
}
結果
Get All Google Account
Success of transfer to another web site
Get All FB Account
最後完整程式碼
class Program
{
static void Main(string[] args)
{
ISsoService service = new SsoService();
Console.WriteLine(service.AccountService.GetAll());
service.TransferAccount();
service.AccountService = new FaceBookAccountService();
Console.WriteLine(service.AccountService.GetAll());
Console.ReadKey();
}
}
public interface IAccountService
{
string GetAll();
void ModifyPwd();
string Login();
bool IsLogin();
void Remove();
}
public interface ISsoService
{
IAccountService AccountService { get; set; }
void TransferAccount();
}
public class SsoService : ISsoService
{
IAccountService _accountService = new GoogleAccountService(); //預設會是google的帳號
public IAccountService AccountService //提供屬性讓外面可以替換
{
get
{
return _accountService;
}
set
{
_accountService = value;
}
}
public void TransferAccount()
{
Console.WriteLine("Success of transfer to another web site");
}
}
public class FaceBookAccountService : IAccountService
{
public string GetAll()
{
return "Get All FB Account";
}
public bool IsLogin()
{
return true;
}
public string Login()
{
return "Anson is login";
}
public void ModifyPwd()
{
Console.WriteLine("Modify success of FB account");
}
public void Remove()
{
Console.WriteLine("Remove success of FB account");
}
}
public class GoogleAccountService : IAccountService
{
public string GetAll()
{
return "Get All Google Account";
}
public bool IsLogin()
{
return true;
}
public string Login()
{
return "Anson is login";
}
public void ModifyPwd()
{
Console.WriteLine("Modify success of google account");
}
public void Remove()
{
Console.WriteLine("Remove success of google account");
}
}
