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模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－facade

名稱	Facade
結(jié)構(gòu)
意圖	為子系統(tǒng)中的一組接口提供一個(gè)一致的界面，F(xiàn) a c a d e 模式定義了一個(gè)高層接口，這個(gè)接口使得這一子系統(tǒng)更加容易使用。
適用性	當(dāng)你要為一個(gè)復(fù)雜子系統(tǒng)提供一個(gè)簡(jiǎn)單接口時(shí)。子系統(tǒng)往往因?yàn)椴粩嘌莼兊迷絹碓綇?fù)雜。大多數(shù)模式使用時(shí)都會(huì)產(chǎn)生更多更小的類。這使得子系統(tǒng)更具可重用性，也更容易對(duì)子系統(tǒng)進(jìn)行定制，但這也給那些不需要定制子系統(tǒng)的用戶帶來一些使用上的困難。F a c a d e 可以提供一個(gè)簡(jiǎn)單的缺省視圖，這一視圖對(duì)大多數(shù)用戶來說已經(jīng)足夠，而那些需要更多的可定制性的用戶可以越過f a c a d e 層。客戶程序與抽象類的實(shí)現(xiàn)部分之間存在著很大的依賴性。引入f a c a d e 將這個(gè)子系統(tǒng)與客戶以及其他的子系統(tǒng)分離，可以提高子系統(tǒng)的獨(dú)立性和可移植性。當(dāng)你需要構(gòu)建一個(gè)層次結(jié)構(gòu)的子系統(tǒng)時(shí)，使用f a c a d e 模式定義子系統(tǒng)中每層的入口點(diǎn)。如果子系統(tǒng)之間是相互依賴的，你可以讓它們僅通過f a c a d e 進(jìn)行通訊，從而簡(jiǎn)化了它們之間的依賴關(guān)系。

Code Example

namespace?Facade_DesignPattern

{

????using?System;

????class?SubSystem_class1?

????{

????????public?void?OperationX()?

????????{

????????????Console.WriteLine("SubSystem_class1.OperationX?called");

????????}

????}

????class?SubSystem_class2

????{

????????public?void?OperationY()

????????{

????????????Console.WriteLine("SubSystem_class2.OperationY?called");

????????}

????}

????class?SubSystem_class3?

????{

????????public?void?OperationZ()

????????{????????????

????????????Console.WriteLine("SubSystem_class3.OperationZ?called");

????????}????

????}

????class?Facade?

????{

????????private?SubSystem_class1?c1?=?new?SubSystem_class1();

????????private?SubSystem_class2?c2?=?new?SubSystem_class2();

????????private?SubSystem_class3?c3?=?new?SubSystem_class3();

????????public?void?OperationWrapper()

????????{

????????????Console.WriteLine("The?Facade?OperationWrapper?carries?out?complex?decision-making");

????????????Console.WriteLine("which?in?turn?results?in?calls?to?the?subsystem?classes");

????????????c1.OperationX();

????????????if?(1==1?/*some?really?complex?decision*/)

????????????{

????????????????c2.OperationY();

????????????}

????????????//?lots?of?complex?code?here?.?.?.

????????????c3.OperationZ();

????????}

????????

????}

????///?<summary>

????///????Summary?description?for?Client.

????///?</summary>

????public?class?Client

????{

??????????public?static?int?Main(string[]?args)

????????{

????????????Facade?facade?=?new?Facade();

????????????Console.WriteLine("Client?calls?the?Facade?OperationWrapper");

????????????facade.OperationWrapper();??????

????????????return?0;

????????}

????}

}

一個(gè)實(shí)際生活的例子:

//?Facade?pattern?--?Real?World?example??

using?System;

namespace?DoFactory.GangOfFour.Facade.RealWorld

{

??//?MainApp?test?application?

??class?MainApp

??{

????static?void?Main()

????{

??????//?Facade?

??????Mortgage?mortgage?=?new?Mortgage();

??????//?Evaluate?mortgage?eligibility?for?customer?

??????Customer?customer?=?new?Customer("Ann?McKinsey");

??????bool?eligable?=?mortgage.IsEligible(customer,125000);

??????

??????Console.WriteLine("\n"?+?customer.Name?+?

??????????"?has?been?"?+?(eligable???"Approved"?:?"Rejected"));

??????//?Wait?for?user?

??????Console.Read();

????}

??}

??//?"Subsystem?ClassA"?

??class?Bank

??{

????public?bool?HasSufficientSavings(Customer?c,?int?amount)

????{

??????Console.WriteLine("Check?bank?for?"?+?c.Name);

??????return?true;

????}

??}

??//?"Subsystem?ClassB"?

??class?Credit

??{

????public?bool?HasGoodCredit(Customer?c)

????{

??????Console.WriteLine("Check?credit?for?"?+?c.Name);

??????return?true;

????}

??}

??//?"Subsystem?ClassC"?

??class?Loan

??{

????public?bool?HasNoBadLoans(Customer?c)

????{

??????Console.WriteLine("Check?loans?for?"?+?c.Name);

??????return?true;

????}

??}

??class?Customer

??{

????private?string?name;

????//?Constructor?

????public?Customer(string?name)

????{

??????this.name?=?name;

????}

????//?Property?

????public?string?Name

????{

??????get{?return?name;?}

????}

??}

??//?"Facade"?

??class?Mortgage

??{

????private?Bank?bank?=?new?Bank();

????private?Loan?loan?=?new?Loan();

????private?Credit?credit?=?new?Credit();

????public?bool?IsEligible(Customer?cust,?int?amount)

????{

??????Console.WriteLine("{0}?applies?for?{1:C}?loan\n",

????????cust.Name,?amount);

??????bool?eligible?=?true;

??????//?Check?creditworthyness?of?applicant?

??????if?(!bank.HasSufficientSavings(cust,?amount))?

??????{

????????eligible?=?false;

??????}

??????else?if?(!loan.HasNoBadLoans(cust))?

??????{

????????eligible?=?false;

??????}

??????else?if?(!credit.HasGoodCredit(cust))?

??????{

????????eligible?=?false;

??????}

??????return?eligible;

????}

??}

Output

MethodA() ----
SubSystemOne Method
SubSystemTwo Method
SubSystemFour Method

MethodB() ----
SubSystemTwo Method
SubSystemThree Method

posted on 2006-01-03 15:48 夢(mèng)在天涯閱讀(877) 評(píng)論(1) 編輯收藏引用所屬分類: Design pattern

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# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－facade 2006-04-24 15:17 夢(mèng)在天涯

在什么情況下使用門面模式
為一個(gè)復(fù)雜子系統(tǒng)提供一個(gè)簡(jiǎn)單接口
提高子系統(tǒng)的獨(dú)立性
在層次化結(jié)構(gòu)中，可以使用Facade模式定義系統(tǒng)中每一層的入口。
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# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－facade 2006-04-24 15:17 夢(mèng)在天涯

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