状态模式

用户需求：

定义一个俱乐部，它的顾客有三个状态：访客（VistorState），会员（MemberState），贵宾（VIPState）。每个顾客都有一个帐户（ClubAccount），帐户上存放顾客的存款，根据存款的不同数量切换会员的级别，其中 0~100 为访客，100~1000为会员，1000 以上为贵宾。当顾客需要俱乐部的服务时，俱乐部将根据顾客的当前级别提供与其级别对应的服务内容。当顾客的存款发生变化时，需要及时对他们的状态进行改变。

相关UML：



具体代码如下：

/// <summary>
/// 环境类
/// </summary>
public class Account
{
public AccountState State { set; get; }
public string Owner { set; get; }
public double Balance { set; get; }

public Account(string owner, double initialAmount)
{
Owner = owner;
Balance = initialAmount;
State = new VistorState(this);  //设置初始状态
}

public void SetBalance(double amount)
{
Balance = amount;

}

//存款
public void Deposit(double amount)
{
Console.WriteLine("存入" + amount);
State.Deposit(amount);
Console.WriteLine("用户状态变为" + State._Statename);
}

//消费
public void Shopping(double amount)
{
Console.WriteLine("消费" + amount);
State.Shopping(amount);
Console.WriteLine("用户状态变为" + State._Statename);
}

}

/// <summary>
/// 抽象状态类
/// </summary>
public abstract class AccountState
{
protected Account _account;
public string _Statename;

public abstract void Deposit(double amount);
public abstract void Shopping(double amount);
public abstract void StateCheck();
}

/// <summary>
/// 访客状态类
/// </summary>
public class VistorState:AccountState
{
public VistorState(Account account)
{
_account = account;
_Statename = "访客账户";
StateCheck();  //默认的检查
}

//取款
public override void Deposit(double amount)
{
_account.Balance += amount;
Console.WriteLine(_account.Owner + " 向账户中存款" + amount + "元，存款后的账户余额为：" + _account.Balance);
StateCheck();
}

//消费
public override void Shopping(double amount)
{
double newBalance = _account.Balance - amount;
if (newBalance > 0)
{
_account.Balance -= amount;
Console.WriteLine(_account.Owner + "在《访客服务》中消费" + amount + "元，账户余额：" + _account.Balance);
}
else
{
Console.WriteLine("您的账户余额不足，请充值。");
}
StateCheck();
}

//检查用户状态
public override void StateCheck()
{
if (_account.Balance > 100 && _account.Balance < 1000)
{
//会员用户状态
_account.State = new MemberState(_account);
}
else if (_account.Balance > 1000)
{
//贵宾用户状态
_account.State = new VIPState(_account);
}
}
}

/// <summary>
/// 会员状态类
/// </summary>
public class MemberState:AccountState
{
public MemberState(Account account)
{
_account = account;
_Statename = "会员账户";
}

//取款
public override void Deposit(double amount)
{
_account.Balance += amount;
Console.WriteLine(_account.Owner + " 向账户中存款" + amount + "元，存款后的账户余额为：" + _account.Balance);
StateCheck();
}

//消费
public override void Shopping(double amount)
{
double newBalance = _account.Balance - amount;
if (newBalance > 0)
{
_account.Balance -= amount;
Console.WriteLine(_account.Owner + "在《会员服务》中消费" + amount + "元，账户余额：" + _account.Balance);
}
else
{
Console.WriteLine("您的账户余额不足，请充值。");
}
StateCheck();
}

//检查用户状态
public override void StateCheck()
{
if (_account.Balance > 0 && _account.Balance < 100)
{
//访客用户状态
_account.State = new VistorState(_account);
}
else if (_account.Balance > 1000)
{
//贵宾用户状态
_account.State = new VIPState(_account);

}
}
}

/// <summary>
/// 贵宾状态类
/// </summary>
public class VIPState:AccountState
{
public VIPState(Account account)
{
_account = account;
_Statename = "贵宾账户";
}

//取款
public override void Deposit(double amount)
{
_account.Balance += amount;
Console.WriteLine(_account.Owner + " 向账户中存款" + amount + "元，存款后的账户余额为：" + _account.Balance);
StateCheck();
}

//消费
public override void Shopping(double amount)
{
double newBalance = _account.Balance - amount;
if (newBalance > 0)
{
_account.Balance -= amount;
Console.WriteLine(_account.Owner + "在《贵宾服务》中消费" + amount + "元，账户余额：" + _account.Balance);
}
else
{
Console.WriteLine("您的账户余额不足，请充值。");
}
StateCheck();
}

//检查用户状态
public override void StateCheck()
{
if (_account.Balance > 0 && _account.Balance < 100)
{
//访客用户状态
_account.State = new VistorState(_account);
}
else if (_account.Balance > 100&&_account.Balance<1000)
{
//会员用户状态
_account.State = new MemberState(_account);
}
}
}

/// <summary>
/// 客户端代码
/// </summary>
class Program
{
static void Main(string[] args)
{
Account account = new Account("王大锤", 99);
Console.WriteLine("开户成功。姓名：" + account.Owner + " 初始金额：" + account.Balance + " 账户类型：" + account.State._Statename);
Console.WriteLine("----------------------------");

account.Deposit(20);
Console.WriteLine("-----------------------------");

account.Shopping(30);
Console.WriteLine("-----------------------------");

account.Deposit(9999);
Console.WriteLine("------------------------------");

Console.ReadLine();
}
}

运行结果如下：