耦合關(guān)系：
??? ???
動機(Motivation):
??? 在軟件系統(tǒng)中，由于需求的變化，"這個對象的具體實現(xiàn)"經(jīng)常面臨著劇烈的變化，但它卻有比較穩(wěn)定的接口。
??? 如何應(yīng)對這種變化呢？提供一種封裝機制來隔離出"這個易變對象"的變化，從而保持系統(tǒng)中"其它依賴的對象"不隨需求的變化而變化。
意圖(Intent):
??? 定義一個用戶創(chuàng)建對象的接口，讓子類決定實例哪一個類。Factory Method使一個類的實例化延遲到子類。
??? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ? ----------《設(shè)計模式》GOF
結(jié)構(gòu)圖(Struct):
??? ?? ?? ?? ???
生活實例：
??? ?? ???
適用性：
??? 1.當一個類不知道它所必須創(chuàng)建的對象類的時候。
??? 2.當一個類希望由它子類來指定它所創(chuàng)建對象的時候。
??? 3.當類將創(chuàng)建對象的職責委托給多個幫助子類中的某個，并且你希望將哪一個幫助子類是代理者這一信息局部化的時候。

實例代碼：
CarFactory類：

1????public?abstract?class?CarFactory
2?????{
3????????public?abstract?Car?CarCreate();
4?????}

Car類：?

1???public?abstract?class?Car
2?????{
3????????public?abstract?void?StartUp();
4????????public?abstract?void?Run();
5????????public?abstract?void?Stop();
6???????
7?????}

HongQiCarFactory類：

1???public?class?HongQiCarFactory:CarFactory
2?????{
3????????public?override?Car?CarCreate()
4????????{
5????????????return?new?HongQiCar();
6????????}
7?????}

BMWCarFactory類：

1???public?class?BMWCarFactory:CarFactory
2?????{
3????????public?override?Car?CarCreate()
4????????{
5????????????return?new?BMWCar();
6????????}
7?????}

HongQiCar類：

?1???public??class?HongQiCar:Car
?2?????{
?3???????public?override?void?StartUp()
?4???????{
?5???????????Console.WriteLine("Test?HongQiCar?start-up?speed!");
?6???????}
?7???????public?override?void?Run()
?8???????{
?9???????????Console.WriteLine("The?HongQiCar?run?is?very?quickly!");
10???????}
11???????public?override?void?Stop()
12???????{
13???????????Console.WriteLine("The?slow?stop?time?is?3?second?");
14???????}
15?????}

BMWCar類：

?1????public??class?BMWCar:Car
?2?????{
?3????????public?override?void?StartUp()
?4????????{
?5????????????Console.WriteLine("The?BMWCar?start-up?speed?is?very?quickly");
?6????????}
?7????????public?override?void?Run()
?8????????{
?9????????????Console.WriteLine("The?BMWCar?run?is?quitely?fast?and?safe!!!");
10????????}
11????????public?override?void?Stop()
12????????{
13????????????Console.WriteLine("The?slow?stop?time?is?2?second");
14????????}
15?????}

app.config

1?<?xml?version="1.0"?encoding="utf-8"??>
2?<configuration>
3???<appSettings>
4?????<add?key="No1"?value="HongQiCarFactory"/>
5?????<add?key="No2"?value="BMWCarFactory"/>
6???</appSettings>
7?</configuration>

Program類:

?1??class?Program
?2?????{
?3?????????static?void?Main(string[]?args)
?4?????????{
?5?????????????Console.WriteLine("Please?Enter?Factory?Method?No:");
?6?????????????Console.WriteLine("******************************");
?7?????????????Console.WriteLine("no?????????Factory?Method");
?8?????????????Console.WriteLine("1??????????HongQiCarFactory");
?9?????????????Console.WriteLine("2??????????BMWCarFactory");
10?????????????Console.WriteLine("******************************");
11?????????????int?no=Int32.Parse(Console.ReadLine().ToString());
12?????????????string?factoryType=ConfigurationManager.AppSettings["No"+no];
13?????????????//CarFactory?factory?=?new?HongQiCarFactory();
14?????????????CarFactory?factory?=?(CarFactory)Assembly.Load("FactoryMehtod").CreateInstance("FactoryMehtod."?+?factoryType);?;
15?????????????Car?car=factory.CarCreate();
16?????????????car.StartUp();
17?????????????car.Run();
18?????????????car.Stop();
19?????????????
20?????????}
21?????}

Factory Method 模式的幾個要點：
Factory Method模式主要用于隔離類對象的使用者和具體類型之間的耦合關(guān)系。面對一個經(jīng)常變化的具體類型，緊耦合關(guān)系會導(dǎo)致軟件的脆弱。
Factory Method模式通過面向?qū)ο蟮氖址?#xff0c;將所要創(chuàng)建的具體對象工作延遲到子類，從而實現(xiàn)一種擴展（而非更改）的策略，較好地解決了這種緊耦合關(guān)系。
Factory Mehtod模式解決"單個對象"的需求變化，AbstractFactory模式解決"系列對象"的需求變化，Builder模式解決"對象部分"的需求變化。

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