Add Visitor pattern

Author: ivandrofly

State/Account.cs

@@ -0,0 +1,51 @@
+using System;
+
+namespace DoFactory.GangOfFour.State.RealWorld
+{
+    /// <summary>
+    /// The 'Context' class
+    /// </summary>
+    public class Account
+    {
+        private State _state;
+        private string _owner;
+
+        // Constructor
+        public Account(string owner)
+        {
+            // New accounts are 'Silver' by default
+            _owner = owner;
+            _state = new SilverState(0.0, this);
+        }
+
+        // Properties
+        public double Balance => _state.Balance;
+
+        public State State { get => _state; set => _state = value; }
+
+        public void Deposit(double amount)
+        {
+            _state.Deposit(amount);
+            Console.WriteLine("Deposited {0:C} --- ", amount);
+            Console.WriteLine(" Balance = {0:C}", Balance);
+            Console.WriteLine(" Status = {0}", State.GetType().Name);
+            Console.WriteLine("");
+        }
+
+        public void Withdraw(double amount)
+        {
+            _state.Withdraw(amount);
+            Console.WriteLine("Withdrew {0:C} --- ", amount);
+            Console.WriteLine(" Balance = {0:C}", Balance);
+            Console.WriteLine(" Status = {0}\n", State.GetType().Name);
+        }
+
+        public void PayInterest()
+        {
+            _state.PayInterest();
+            Console.WriteLine("Interest Paid --- ");
+            Console.WriteLine(" Balance = {0:C}", Balance);
+            Console.WriteLine(" Status = {0}\n", State.GetType().Name);
+        }
+    }
+}

State/Program.cs

@@ -1,15 +1,28 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace State
+namespace DoFactory.GangOfFour.State.RealWorld
 {
-    class Program
+    /// <summary>
+    /// MainApp startup class for Real-World 
+    /// State Design Pattern.
+    /// </summary>
+    class MainApp
     {
-        static void Main(string[] args)
+        /// <summary>
+        /// Entry point into console application.
+        /// </summary>
+        static void Main()
         {
+            // Open a new account
+            Account account = new Account("Jim Johnson");
+            // Apply financial transactions
+            account.Deposit(500.0);
+            account.Deposit(300.0);
+            account.Deposit(550.0);
+            account.PayInterest();
+            account.Withdraw(2000.00);
+            account.Withdraw(1100.00);
+            // Wait for user
+            Console.ReadKey();
         }
     }
 }

State/State.cs

@@ -0,0 +1,34 @@
+namespace DoFactory.GangOfFour.State.RealWorld
+{
+    /// <summary>
+    /// The 'State' abstract class
+    /// </summary>
+    public abstract class State
+    {
+        protected Account account;
+        protected double balance;
+        protected double interest;
+        protected double lowerLimit;
+        protected double upperLimit;
+
+        // Properties
+        public Account Account
+        {
+            get { return account; }
+            set { account = value; }
+        }
+
+        public double Balance
+        {
+            get { return balance; }
+            set { balance = value; }
+        }
+
+        public abstract void Deposit(double amount);
+
+        public abstract void Withdraw(double amount);
+
+        public abstract void PayInterest();
+
+    }
+}

State/State.csproj

@@ -42,8 +42,13 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Account.cs" />
+    <Compile Include="GoldState.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="RedState.cs" />
+    <Compile Include="SilverState.cs" />
+    <Compile Include="State.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="App.config" />

State/States/GoldState.cs

@@ -0,0 +1,62 @@
+namespace DoFactory.GangOfFour.State.RealWorld
+{
+    /// <summary>
+    /// A 'ConcreteState' class
+    /// <remarks>
+    /// Gold indicates an interest bearing state
+    /// </remarks>
+    /// </summary>
+    public class GoldState : State
+    {
+        // Overloaded constructors
+        public GoldState(State state)
+          : this(state.Balance, state.Account)
+        {
+        }
+
+        public GoldState(double balance, Account account)
+        {
+            this.balance = balance;
+            this.account = account;
+            Initialize();
+        }
+
+        private void Initialize()
+        {
+            // Should come from a database
+            interest = 0.05;
+            lowerLimit = 1000.0;
+            upperLimit = 10000000.0;
+        }
+
+        public override void Deposit(double amount)
+        {
+            balance += amount;
+            StateChangeCheck();
+        }
+
+        public override void Withdraw(double amount)
+        {
+            balance -= amount;
+            StateChangeCheck();
+        }
+
+        public override void PayInterest()
+        {
+            balance += interest * balance;
+            StateChangeCheck();
+        }
+
+        private void StateChangeCheck()
+        {
+            if (balance < 0.0)
+            {
+                account.State = new RedState(this);
+            }
+            else if (balance < lowerLimit)
+            {
+                account.State = new SilverState(this);
+            }
+        }
+    }
+}

State/States/RedState.cs

@@ -0,0 +1,57 @@
+using System;
+
+namespace DoFactory.GangOfFour.State.RealWorld
+{
+    /// <summary>
+    /// A 'ConcreteState' class
+    /// <remarks>
+    /// Red indicates that account is overdrawn 
+    /// </remarks>
+    /// </summary>
+    public class RedState : State
+    {
+        private double _serviceFee;
+        // Constructor
+        public RedState(State state)
+        {
+            balance = state.Balance;
+            account = state.Account;
+            Initialize();
+
+        }
+
+        private void Initialize()
+        {
+            // Should come from a datasource
+            interest = 0.0;
+            lowerLimit = -100.0;
+            upperLimit = 0.0;
+            _serviceFee = 15.00;
+        }
+
+        public override void Deposit(double amount)
+        {
+            balance += amount;
+            StateChangeCheck();
+        }
+
+        public override void Withdraw(double amount)
+        {
+            amount -= _serviceFee;
+            Console.WriteLine("No funds available for withdrawal!");
+        }
+
+        public override void PayInterest()
+        {
+            // No interest is paid
+        }
+
+        private void StateChangeCheck()
+        {
+            if (balance > upperLimit)
+            {
+                account.State = new SilverState(this);
+            }
+        }
+    }
+}

State/States/SilverState.cs

@@ -0,0 +1,64 @@
+namespace DoFactory.GangOfFour.State.RealWorld
+{
+    /// <summary>
+    /// A 'ConcreteState' class
+    /// <remarks>
+    /// Silver indicates a non-interest bearing state
+    /// </remarks>
+    /// </summary>
+    public class SilverState : State
+    {
+        // Overloaded constructors
+        public SilverState(State state) :
+          this(state.Balance, state.Account)
+        {
+        }
+
+        public SilverState(double balance, Account account)
+        {
+            this.balance = balance;
+            this.account = account;
+            Initialize();
+        }
+
+        private void Initialize()
+        {
+            // Should come from a datasource
+            interest = 0.0;
+            lowerLimit = 0.0;
+            upperLimit = 1000.0;
+        }
+
+        public override void Deposit(double amount)
+        {
+            balance += amount;
+            StateChangeCheck();
+        }
+
+        public override void Withdraw(double amount)
+        {
+            balance -= amount;
+            StateChangeCheck();
+        }
+
+        public override void PayInterest()
+        {
+            balance += interest * balance;
+            StateChangeCheck();
+        }
+
+        private void StateChangeCheck()
+        {
+            // account.State = balance < lowerLimit ? new RedState(this) : new GoldState(this);
+            if (balance < lowerLimit)
+            {
+                account.State = new RedState(this);
+            }
+            else
+            {
+                account.State = new GoldState(this);
+            }
+        }
+
+    }
+}