设计模式：工厂方法模式（Factory Method）

定义：定义一个用于创建对象的接口，让子类决定实例化哪一个类。

         工厂方法使一个类的实例化延迟到其子类。

结构图：

示例：

HTML代码：

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:TextBox runat="server" ID="txtNumberA"></asp:TextBox>
        <asp:DropDownList runat="server" ID="ddlType">
            <asp:ListItem Selected="True">+</asp:ListItem>
            <asp:ListItem>-</asp:ListItem>
            <asp:ListItem>*</asp:ListItem>
            <asp:ListItem>/</asp:ListItem>
        </asp:DropDownList>
        <asp:TextBox runat="server" ID="txtNumberB"></asp:TextBox>
        =
        <asp:TextBox runat="server" ID="txtResult"></asp:TextBox>
        <asp:Button runat="server" ID="btnCalculate" Text="计算" OnClick="btnCalculate_Click" />
        <asp:Label runat="server" ID="lblMsg"></asp:Label>
    </div>
    </form>
</body>
</html>
View Code

IFactory.cs:
 interface IFactory
    {
        Operation CreateOpertion();
    }

AddFactory.cs:

 public class AddFactory : IFactory
    {
        public Operation CreateOpertion()
        {
            return new OperateAdd();
        }
    }

SubFactory.cs:

 public class SubFactory : IFactory
    {
        public Operation CreateOpertion()
        {
            return new OperateSub();
        }
    }

MulFactory.cs:

 public class MulFactory : IFactory
    {
        public Operation CreateOpertion()
        {
            return new OperateMul();
        }
    }

DivFactory.cs:

 public class DivFactory : IFactory
    {
        public Operation CreateOpertion()
        {
            return new OperateDiv();
        }
    }

Operation.cs:

 public class Operation
    {
        public int NumberA { get; set; }

        public int NumberB { get; set; }

        public virtual int GetResult()
        {
            return 0;
        }
    }
View Code

OperateAdd.cs:

 public class OperateAdd : Operation
    {
        public override int GetResult()
        {
            return NumberA + NumberB;
        }
    }
View Code

OperateSub.cs:

public class OperateSub : Operation
    {
        public override int GetResult()
        {
            return NumberA - NumberB;
        }
    }
View Code

OperateMul.cs:

 public class OperateMul : Operation
    {
        public override int GetResult()
        {
            return NumberA * NumberB;
        }
    }
View Code

OperateDiv.cs:

 public class OperateDiv : Operation
    {
        public override int GetResult()
        {
            int result = 0;

            if (NumberB == 0)
                throw new Exception("被除数为0！");

            result = NumberA / NumberB;

            return result;
        }
    }
View Code

客户端代码：

  protected void btnCalculate_Click(object sender, EventArgs e)
        {
            IFactory factory = null;

            string type = ddlType.SelectedValue;
            switch (type)
            {
                case "+":
                    factory = new AddFactory();
                    break;
                case "-":
                    factory = new SubFactory();
                    break;
                case "*":
                    factory = new MulFactory();
                    break;
                case "/":
                    factory = new DivFactory();
                    break;
            }

            try
            {
                Operation operation = factory.CreateOpertion();
                operation.NumberA = Convert.ToInt32(txtNumberA.Text);
                operation.NumberB = Convert.ToInt32(txtNumberB.Text);

                txtResult.Text = operation.GetResult().ToString();
            }
            catch (Exception ex)
            {

                lblMsg.Text = ex.Message;
            }


        }
View Code

简单工厂模式和工厂方法模式比较：

简单工厂：最大优点在于工厂类中包含了必要的逻辑判断，根据客户端的选择条件动态实例化相应的类，对于客户端来说，

              去除了与具体产品的依赖。（违反了开闭原则）

工厂方法：将必要的判断逻辑放在客户端，这样在增加新的产品类时只需要增加相应的工厂类，而不需要修改原来的类，遵

               守了开闭原则。

 

 

 

 

posted @ 2014-02-11 11:16  齐_大圣  阅读(376)  评论(0)  编辑  收藏  举报