设计模式中工厂模式实际体验

 

 使用工厂模式以前, 绘制每个图元时都要使用new操作符进行实例化, 具体如下:

public static void OnMouseDown(object sender, MouseEventArgs e)
        {
            NCControl ncControl = sender as NCControl;
            startPoint = new Point(e.X, e.Y);
            switch (ncControl.CurrentOperator)
            {
                case Operator.Line:
                    ncControl.CurrentShape = new Line();    //实例化
                    ncControl.CurrentShape.Pen = ncControl.CurrentPen;
                    break;
                case Operator.Ellipse:
                    ncControl.CurrentShape = new Ellipse(); //实例化
                    ncControl.CurrentShape.Pen = ncControl.CurrentPen;
                    break;
                default:
                    break;
            }
        }

结果是很不爽!!

用了工厂模式以后呢, 上面的代码就变成如下样子啦:

  public static void OnMouseDown(object sender, MouseEventArgs e)
        {
            NCControl ncControl = sender as NCControl;
            startPoint = new Point(e.X, e.Y);
            //使用抽象工厂设计模式后，switch代码段就可以去掉了！
            string shapename = ncControl.CurrentOperator.ToString();
            ncControl.CurrentShape = ShapeFactory.CreateShape(shapename); 
            ncControl.CurrentShape.Pen = ncControl.CurrentPen;
        }

是不是很简洁呢。

这其中的奥秘也就在ShapeFactory抽象工厂类中：

public abstract class ShapeFactory
    {
        public static IShape CreateShape(string name)
        {
            try
            {
                string typename = "你的命名空间."+ name;  
                Type shapetype = Type.GetType(typename, true);
                IShape shape = Activator.CreateInstance(shapetype) as IShape;
                return shape;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(ex.Message);
            }
            return null;
        }
    }

类继承关系如下：

IShape-->SimpleShape--> Line/Ellipse/....

如果您对工厂模式不熟，可以参考： http://www.qqgb.com/Program/CCC/CCCSJ/Program_56488.html