设计模式之状态State
参考http://blog.jobbole.com/78126/
State模式的定义: 不同的状态,不同的行为;或者说,每个状态有着相应的行为.
State模式在实际使用中比较多,适合"状态的切换".
因为我们经常会使用If elseif else 进行状态切换,
如果针对状态的这样判断切换反复出现,我们就要联想到是否可以采取State模式了.
不只是根据状态,也有根据属性.如果某个对象的属性不同,对象的行为就不一样,
这点在数据库系统中出现频率比较高,我们经常会在一个数据表的尾部,
加上property属性含义的字段,用以标识记录中一些特殊性质的记录,
这种属性的改变(切换)又是随时可能发生的,就有可能要使用State.
State模式=状态+行为
if (which==1) state="hello"; else if (which==2) state="hi";else if (which==3) state="bye";
这就是 "开关切换状态",是将state的状态从"hello"切换到"hi",再切换到""bye";在切换到"hello",
好象一个旋转开关,这种状态改变就可以使用State模式了.
如果单纯有上面一种将"hello"-->"hi"-->"bye"-->"hello"这一个方向切换,也不一定需要使用State模式,
因为State模式会建立很多子类,复杂化,但是如果又发生另外一个行为:
将上面的切换方向反过来切换,或者需要任意切换,就需要State了
例如: 经典的TcpConnection, Tcp的状态有创建 侦听 关闭三个,并且反复转换,其创建 侦听 关闭的具体行为不是简单一两句就能完成的,适合使用State
例如:信箱POP帐号, 会有四种状态, start HaveUsername Authorized quit,每个状态对应的行为应该是比较大的.适合使用State
例如:在工具箱挑选不同工具,可以看成在不同工具中切换,适合使用State.如 具体绘图程序,用户可以选择不同工具绘制方框 直线 曲线,这种状态切换可以使用State.
/// <summary>
/// 测试
/// </summary>
public class StateMode
{
public StateMode()
{
Account acc = new Account("风动破");
acc.Deposit(1000);
acc.Deposit(200);
acc.PayInterst();
acc.WithDraw(10000);
acc.WithDraw(100);
acc.PayInterst();
}
}
public class Account
{
public State State;
private string owner;
public double Balance { get { return State.balance; } }
public Account(string owner)
{
this.owner = owner;
this.State = new SilverState(0.0, this);
Console.WriteLine(owner+"开户成功！\n");
}
/// <summary>
/// 存钱
/// </summary>
public void Deposit(double amount)
{
State.Deposit(amount);
Console.WriteLine("存款金额为 {0:C}——", amount);
Console.WriteLine("账户余额为 =:{0:C}", this.Balance);
Console.WriteLine("账户状态为: {0}", this.State.GetType().Name);
Console.WriteLine();
}
/// <summary>
/// 取钱
/// </summary>
public void WithDraw(double amount)
{
State.WithDraw(amount);
Console.WriteLine("取款金额为 {0:C}——", amount);
Console.WriteLine("账户余额为 =:{0:C}", this.Balance);
Console.WriteLine("账户状态为: {0}", this.State.GetType().Name);
Console.WriteLine();
}
/// <summary>
/// 获得利息
/// </summary>
public void PayInterst()
{
State.PayInterst();
Console.WriteLine("Interest Paid --- ");
Console.WriteLine("账户余额为 =:{0:C}", this.Balance);
Console.WriteLine("账户状态为: {0}", this.State.GetType().Name);
Console.WriteLine();
}
}
public abstract class State {
public Account myAccount;//用户
public double balance;//余额
public double interst;//利率
public double maxLimit;//最大值
public double minLimit;//最小值
/// <summary>
/// 存钱
/// </summary>
public abstract void Deposit(double amount);
/// <summary>
/// 取钱
/// </summary>
public abstract void WithDraw(double amount);
/// <summary>
/// 支付利息
/// </summary>
public abstract void PayInterst();
}
/// <summary>
/// 赤字状态:
/// </summary>
public class RedState : State
{
public RedState(State state)
{
this.balance = state.balance;
this.myAccount = state.myAccount;
interst = 0;
minLimit = -3000;
maxLimit = 0;
}
public override void Deposit(double amount)
{
balance += amount;
StateChangeCheck();
}
public override void WithDraw(double amount)
{
Console.WriteLine("当前赤字状态，没有钱可以用了");
}
public override void PayInterst()
{
}
private void StateChangeCheck()
{
if (balance > maxLimit)
{
myAccount.State = new SilverState(this);
}
}
}
public class SilverState : State {
private double p;
private Account account;
public SilverState(State state):this(state.balance,state.myAccount){
}
public SilverState(double p, Account account)
{
// TODO: Complete member initialization
this.balance = p;
this.myAccount = account;
interst = 0;
minLimit = 0;
maxLimit = 1000;
}
public override void Deposit(double amount)
{
balance += amount;
StateChangeCheck();
}
public override void WithDraw(double amount)
{
balance -= amount;
StateChangeCheck();
}
public override void PayInterst()
{
balance += balance * interst;
StateChangeCheck();
}
private void StateChangeCheck()
{
if (balance < minLimit)
myAccount.State = new RedState(this);
else if (balance > maxLimit)
myAccount.State = new GoldState(this);
}
}
public class GoldState : State {
public GoldState(State state)
{
this.balance = state.balance;
this.myAccount = state.myAccount;
interst = 0.05;
minLimit = 1000;
maxLimit = 1000000;
}
public override void Deposit(double amount)
{
balance += amount;
StateChangeCheck();
}
public override void WithDraw(double amount)
{
balance -= amount;
StateChangeCheck();
}
public override void PayInterst()
{
balance += balance * interst;
StateChangeCheck();
}
private void StateChangeCheck()
{
if (balance < 0)
myAccount.State = new RedState(this);
else if (balance < minLimit)
myAccount.State = new SilverState(this);
}
}
===============================================================
/// <summary>
/// 中介+状态 测试类
/// </summary>
public class MediatorState
{
public MediatorState()
{
AbstractPart part1 = new Apart();
AbstractPart part2 = new Bpart();
part1.money = 100;
part2.money = 100;
IMediator mediator = new MyMediator(new InitState());
mediator.Enter(part1);
mediator.Enter(part2);
mediator.state = new AWinState(mediator);
mediator.changeMoney(5);
Console.WriteLine("A 现在的钱是：{0}", part1.money);// 应该是95
Console.WriteLine("B 现在的钱是：{0}", part2.money); // 应该是105
mediator.state = new BWinState(mediator);
mediator.changeMoney(10);
Console.WriteLine("A 现在的钱是：{0}", part1.money);// 应该是105
Console.WriteLine("B 现在的钱是：{0}", part2.money); // 应该是95
}
}
/// <summary>
/// 牌局
/// </summary>
public abstract class AbstractPart
{
public int money;
public AbstractPart() {
money = 0;
}
public abstract void changeMeoney(int money ,IMediator mediator);
}
/// <summary>
/// A牌
/// </summary>
public class Apart : AbstractPart
{
public override void changeMeoney(int money, IMediator mediator)
{
mediator.changeMoney(money);
}
}
/// <summary>
/// B牌
/// </summary>
public class Bpart : AbstractPart
{
public override void changeMeoney(int money, IMediator mediator)
{
mediator.changeMoney(money);
}
}
/// <summary>
/// 建立平台：加人、减人、计算得分
/// </summary>
public abstract class IMediator {
public List<AbstractPart> list = new List<AbstractPart>();
public IState state;
public IMediator(IState state) {
this.state = state;
}
public void changeMoney(int money) {
state.changemoney(money);
}
public void Enter(AbstractPart part)
{
list.Add(part);
}
public void Remove(AbstractPart part) {
list.Remove(part);
}
}
public class MyMediator:IMediator {
public MyMediator(IState STATE) : base(STATE) { }
}
/// <summary>
/// 状态
/// </summary>
public abstract class IState
{
protected IMediator mediator;
public abstract void changemoney(int mon);
}
/// <summary>
/// 初始状态
/// </summary>
public class InitState : IState {
public InitState() {
Console.WriteLine("Start！");
}
public override void changemoney(int mon)
{
return;
}
}
/// <summary>
/// AWin状态计算得分,平台人员筛选
/// </summary>
public class AWinState : IState {
public AWinState(IMediator mediators)
{
// TODO: Complete member initialization
this.mediator = mediators;
}
public override void changemoney(int mon)
{
foreach (AbstractPart p in mediator.list)
{
Bpart b = p as Bpart;
// 如果集合对象中时B对象，则对B的钱添加
if (b != null)
{
b.money += mon;
}
else
{
p.money -= mon;
}
}
}
}
/// <summary>
/// BWin状态计算得分,平台人员筛选
/// </summary>
public class BWinState : IState
{
public BWinState(IMediator mediators)
{
// TODO: Complete member initialization
this.mediator = mediators;
}
public override void changemoney(int mon)
{
foreach (AbstractPart p in mediator.list)
{
Apart b = p as Apart;
// 如果集合对象中时B对象，则对B的钱添加
if (b != null)
{
b.money += mon;
}
else
{
p.money -= mon;
}
}
}
}
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