状态模式实例

用户需求：

设计思路：

1.UML图

具体代码实现：

抽象状态类

AccountState类

    public abstract class AccountState
    {
        protected clubAccount Account;
        //存款
        public abstract void Deposit(double amount);
        //消费
        public abstract void Consume(double amount);
        //检查账户状态
        public abstract void StateCheck();

    }

　　具体状态类

     VistorState类

public class VistorState : AccountState
    {
        public VistorState(clubAccount account)
        {
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Account.Balance += amount;
            Console.WriteLine("向名为"+Account.Owner+"的账户中存款"+amount+"元，存款后账户余额为"+Account.Balance+"元");
            StateCheck();
        }
        public override void Consume(double amount)
        {
            double newBalance = Account.Balance - amount;
            if (newBalance > 0)
            {
                Account.Balance = newBalance;
                Console.WriteLine("向名为" + Account.Owner + "的账户中消费" + amount + "元，存款后账户余额为" + Account.Balance + "元");
                StateCheck();
            }
            else
            {
                Console.WriteLine("你的账户余额不足,无法消费,请先存款");
            }
            StateCheck();
        }
        public override void StateCheck()
        {
            if (Account.Balance > 100 && Account.Balance <= 1000)
            {
                Account.State = new MenberState(Account);
            }
            else if (Account.Balance > 1000)
            {
                Account.State = new VIPState(Account);
            }
        }
    }

　　MenberState类

public class MenberState : AccountState
    {
        public MenberState(clubAccount account)
        {
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Account.Balance += amount;
            Console.WriteLine("向名为" + Account.Owner + "的账户中存款" + amount + "元，存款后账户余额为" + Account.Balance + "元");
            StateCheck();
        }
        public override void Consume(double amount)
        {
            double newBalance = Account.Balance - amount;
            if (newBalance > 0)
            {
                Account.Balance = newBalance;
                Console.WriteLine("向名为" + Account.Owner + "的账户中消费" + amount + "元，存款后账户余额为" + Account.Balance + "元");
                StateCheck();
            }
            else
            {
                Console.WriteLine("你的账户余额不足,无法消费,请先存款");
            }
            StateCheck();
        }
        public override void StateCheck()
        {
            if (Account.Balance > 0&& Account.Balance <= 100)
            {
                Account.State = new VistorState(Account);
            }
            else if (Account.Balance > 1000)
            {
                Account.State = new VIPState(Account);
            }
        }
    }

　　VIPState类

public class VIPState : AccountState
    {
        public VIPState(clubAccount account)
        {
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Account.Balance += amount;
            Console.WriteLine("向名为" + Account.Owner + "的账户中存款" + amount + "元，存款后账户余额为" + Account.Balance + "元");
            StateCheck();
        }
        public override void Consume(double amount)
        {
            double newBalance = Account.Balance - amount;
            if (newBalance > 0)
            {
                Account.Balance = newBalance;
                Console.WriteLine("向名为" + Account.Owner + "的账户中消费" + amount + "元，存款后账户余额为" + Account.Balance + "元");
                StateCheck();
            }
            else
            {
                Console.WriteLine("你的账户余额不足,无法消费,请先存款");
            }
            StateCheck();
        }
        public override void StateCheck()
        {
            if (Account.Balance > 0 && Account.Balance <= 100)
            {
                Account.State = new VistorState(Account);
            }
            else if (Account.Balance >100 && Account.Balance<=1000)
            {
                Account.State = new MenberState(Account);
            }
        }
    }

　　环境类

     clubAccount类

public class clubAccount
    {
        public AccountState State { get; set; }
        public double Balance { get; set; }
        public string Owner { get; set; }
        public clubAccount(string owner, double initialAmount)
        {
            Owner = owner;
            Balance = initialAmount;
            State = new VistorState(this);
        }

        public void SetBalance(double amount)
        {
            Balance = amount;
        }
        public void Deposit(double amount)
        {
            Console.WriteLine("现要存款" + amount + "元");
            State.Deposit(amount);
            Console.WriteLine("账户状态变为" + State);
        }
        public void Consume(double amount)
        {
            Console.WriteLine("现要消费" + amount + "元");
            State.Consume(amount);
            Console.WriteLine("账户状态变为" + State);
 
        }
        
    }

　　客户端

static void Main(string[] args)
        {
            clubAccount account = new clubAccount("张三", 0);
            Console.WriteLine("开户成功，姓名:" + account.Owner + ",初始金额:" + account.Balance);
            Console.WriteLine("------------------------");

            account.Deposit(50);
            Console.WriteLine("------------------------");
            account.Deposit(100);
            Console.WriteLine("------------------------");
           account.Deposit(1000);
            Console.WriteLine("------------------------");
            account.Consume(500);
            Console.WriteLine("------------------------");
            account.Consume(200);
            Console.WriteLine("------------------------");
            account.Consume(400);
            Console.WriteLine("------------------------");
            account.Consume(100);
            Console.WriteLine("------------------------");
            Console.ReadLine();




        }

　　运行结果

      总结

      优点：封装了转换规则

              将所有与某个状态有关的行为放到一个类中，并且可以方便地增加新的状态，只需要改变对象状态即可改变对象的行为    

              允许状态转换逻辑与状态对象合为一体，而不是某一个巨大的条件语句块
              可以让多个环境对象共享一个状态对象，从而减少系统中对象的个数

      缺点：状态模式的使用必然会增加系统类和对象的个数

               状态模式的结构与实现都较为复杂，如果使用不当将导致程序结构与代码的混乱

               状态模式对“开闭原则”的支持并不太好，对于可以切换状态的状态模式，增加新的状态

类需要修改那些负责状态转换的源代码，否则无法切换到新增状态；而且修改某个状态类的行为也需修改对应类的源代码