简单工厂(Simple Factory)模式又可以叫做：静态工厂方法(Static Factory Method)，它是类的创建模式。
场景：画图程序，画圆，矩形，三角，等等。
方案：需要客户端由一个指定的工厂方法来创建各种画图类。客户端不需要知道各个画图类的名称，
只需要给工厂方法传入画图类的参数，如：circle, square, triangle, etc，这些参数是固定的。
如果画图类改变，甚至类名改变，我们只需要改变工厂方法即可。客户端可以保持不变。
因为，在实际应用中，客户端可能会有成百上千，如果客户端知道的具体细节越多，改动就越大。
首先，我们可以定义一个画图的接口，如下：
namespace designpattern.cs.SimpleFactory
{
public interface IShape
{
void draw();
void erase();
}
}
{
public interface IShape
{
void draw();
void erase();
}
}
第二步，我们可以建立各个画图类，如下：
a) 圆
using System;
namespace designpattern.cs.SimpleFactory
{
public class Circle:IShape
{
public void draw()
{
Console.WriteLine("Draw Circle
");
}
public void erase()
{
Console.WriteLine("Erase Circle ");
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class Circle:IShape
{
public void draw()
{
Console.WriteLine("Draw Circle
}
public void erase()
{
Console.WriteLine("Erase Circle
}
}
}
b) 矩形
using System;
namespace designpattern.cs.SimpleFactory
{
public class Rectangle : IShape
{
public void draw()
{
Console.WriteLine("Draw Rectangle ");
}
public void erase()
{
Console.WriteLine("Erase Rectangle ");
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class Rectangle : IShape
{
public void draw()
{
Console.WriteLine("Draw Rectangle
}
public void erase()
{
Console.WriteLine("Erase Rectangle
}
}
}
c) 三角
using System;
namespace designpattern.cs.SimpleFactory
{
public class Triangle : IShape
{
public void draw()
{
Console.WriteLine("Draw Triangle ");
}
public void erase()
{
Console.WriteLine("Erase Triangle ");
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class Triangle : IShape
{
public void draw()
{
Console.WriteLine("Draw Triangle
}
public void erase()
{
Console.WriteLine("Erase Triangle
}
}
}
我们要考虑到一种情况就是，当客户端输入一个无效的图形参数的时候，
因此，我们要准备一个未知图形类，如下：
using System;
namespace designpattern.cs.SimpleFactory
{
public class UnknownShape : IShape
{
public void draw()
{
Console.WriteLine("Draw Unknown Shape ");
}
public void erase()
{
Console.WriteLine("Erase Unknown Shape ");
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class UnknownShape : IShape
{
public void draw()
{
Console.WriteLine("Draw Unknown Shape
}
public void erase()
{
Console.WriteLine("Erase Unknown Shape
}
}
}
接下来，我们便可以构造我们的工厂类了，如下：
using System;
namespace designpattern.cs.SimpleFactory
{
public class ShapeFactory
{
public static IShape Create(string shape)
{
switch (shape.ToUpper())
{
case "CIRCLE":
return new Circle();
case "RECTANGLE":
return new Rectangle();
case "TRIANGLE":
return new Triangle();
default:
return new UnknownShape();
}
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class ShapeFactory
{
public static IShape Create(string shape)
{
switch (shape.ToUpper())
{
case "CIRCLE":
return new Circle();
case "RECTANGLE":
return new Rectangle();
case "TRIANGLE":
return new Triangle();
default:
return new UnknownShape();
}
}
}
}
最后，我们可以构造一个客户端来试试，如下：
using System;
namespace designpattern.cs.SimpleFactory
{
public class ClientDemo1
{
static void Main(string[] args)
{
IShape shape;
//draw circle
shape = ShapeFactory.Create("circle");
shape.draw();
shape.erase();
//draw rectangle
shape = ShapeFactory.Create("rectangle");
shape.draw();
shape.erase();
//draw unknown
shape = ShapeFactory.Create("diamond");
shape.draw();
shape.erase();
Console.ReadLine();
}
}
}
namespace designpattern.cs.SimpleFactory
{
public class ClientDemo1
{
static void Main(string[] args)
{
IShape shape;
//draw circle
shape = ShapeFactory.Create("circle");
shape.draw();
shape.erase();
//draw rectangle
shape = ShapeFactory.Create("rectangle");
shape.draw();
shape.erase();
//draw unknown
shape = ShapeFactory.Create("diamond");
shape.draw();
shape.erase();
Console.ReadLine();
}
}
}
输出结果：
draw circle ...
erase circle ...
draw rectangle ...
erase rectangle ...
draw Unknown Shape ...
erase Unknown Shape ...