[C# 디자인 패턴] 팩토리 메소드 패턴 예제 (Factory Pattern)

[C# 디자인 패턴] 팩토리 메소드 패턴 예제 (Factory Pattern)

출처 - Factory Method Design Pattern (코드 프로젝트) [링크]

컨셉 요약 - 책 유통 업체가 전국으로 배송하기 위해 3개의 대리점을 개설.

[C# 디자인패턴] 팩토리 메소드패턴

제품을 전달하는 BookStore 클래는 동부, 중부, 서부의 ShipBook() 함수를 몰라도 상관없습니다. BookStore.IDistributor이란 코드를 이용하면 되기 때문이죠. 실제론 아래처럼 사용할 수 있습니다.

IDistributor b = bookStore.GetDistributor();
//the client gets the distributor without having
//to know which distributor is being used

좀 더, 깊숙이 들어가면 아래처럼 UML이 변경됩니다. BookStore가 두 개라면 말이죠.

[C# 디자인패턴] 팩토리 메소드패턴

이럴 경우엔 위의 코드를 조금 수정해 줍니다.

//this client code will not need to be changed even
//if the logic for the distributor changed
public void ShipBook(IBookStore s)    
{        
    IDistributor d = s.GetDistributor();
    d.ShipBook();
}

요약하자면 이런 형태가 되는 것이죠.

[C# 디자인패턴] 팩토리 메소드패턴

아래는 전체 코드입니다.

public enum CustomerLocation { EastCoast, MidWest, WestCoast }
class Program
{     
    static void Main(string[] args)
    {
        Console.WriteLine("East Coast Customer:");
        IBookStore bookstore = new BookStoreA(CustomerLocation.EastCoast);
        ShipBook(bookstore);
 
        Console.WriteLine("Mid West Customer:");
        bookstore = new BookStoreA(CustomerLocation.MidWest);
        ShipBook(bookstore);
 
        Console.WriteLine("West Coast Customer:");
        bookstore = new BookStoreA(CustomerLocation.WestCoast);
        ShipBook(bookstore);
    }
 
    //**** client code does not need to be changed  ***
    private static void ShipBook(IBookStore s)
    {
        IDistributor d = s.GetDistributor();
        d.ShipBook();
    }
}
 
//the factory
public interface IBookStore
{
    IDistributor GetDistributor();
}
 
//concrete factory
public class BookStoreA : IBookStore
{
    private CustomerLocation location;
 
    public BookStoreA(CustomerLocation location)
    {
        this.location = location;
    }
 
    IDistributor IBookStore.GetDistributor()
    {
        //internal logic on which distributor to return
        //*** logic can be changed without changing the client code  ****
        switch (location)
        {
            case CustomerLocation.EastCoast:
                return new EastCoastDistributor();
            case CustomerLocation.MidWest:
                return new MidWestDistributor();
            case CustomerLocation.WestCoast:
                return new WestCoastDistributor();
        }
        return null;
    }
}
 
//the product
public interface IDistributor
{
    void ShipBook();
}
 
//concrete product
public class EastCoastDistributor : IDistributor
{
    void IDistributor.ShipBook()
    {
        Console.WriteLine("Book shipped by East Coast Distributor");
    }
}
 
//concrete product
public class MidWestDistributor : IDistributor
{
    void IDistributor.ShipBook()
    {
        Console.WriteLine("Book shipped by Mid West Distributor");
    }
}
 
//conceret product
public class WestCoastDistributor : IDistributor
{
    void IDistributor.ShipBook()
    {
        Console.WriteLine("Book shipped by West Coast Distributor");
    }
}

[C# 디자인패턴] 팩토리 메소드패턴

[C# 디자인 패턴] 팩토리 메소드 패턴 예제 (Factory Pattern)