31天重构系列笔记

31 31 Days of Refactoring 31 31 2009 10 Sean Chambers blog Tips WPF 31 Tips 31 Sean Chambers 31 http://www.lostechies.com/blogs/sean_chambers/archive/2009/07/31/31-days-of-refactoring.aspx http://github.com/schambers/days-of-refactoring Sean Chambers 1 2 3 1. IList IList using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.EncapsulateCollection.Before { public class Order { private List _orderLines; private double _orderTotal; public IList OrderLines { get { return _orderLines; } } public void AddOrderLine(OrderLine orderLine) { _orderTotal += orderLine.Total; _orderLines.Add(orderLine); } public void RemoveOrderLine(OrderLine orderLine) { orderLine = _orderLines.Find(o => o == orderLine); if (orderLine == null) return; _orderTotal -= orderLine.Total; _orderLines.Remove(orderLine); } } public class OrderLine { public double Total { get; private set; } } } IList IEnumerable IEnumerator GetEnumerator() using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.EncapsulateCollection.After { public class Order { private List _orderLines; private double _orderTotal; public IEnumerable OrderLines { get { return _orderLines; } } public void AddOrderLine(OrderLine orderLine) { _orderTotal += orderLine.Total; _orderLines.Add(orderLine); } public void RemoveOrderLine(OrderLine orderLine) { orderLine = _orderLines.Find(o => o == orderLine); if (orderLine == null) return; _orderTotal -= orderLine.Total; _orderLines.Remove(orderLine); } } public class OrderLine { public double Total { get; private set; } } } SOA 2. namespace LosTechies.DaysOfRefactoring.MoveMethod.Before { public class BankAccount { public BankAccount(int accountAge, int creditScore, AccountInterest accountInterest) { AccountAge = accountAge; CreditScore = creditScore; AccountInterest = accountInterest; } public int AccountAge { get; private set; } public int CreditScore { get; private set; } public AccountInterest { private set; } 4 public AccountInterest AccountInterest { get; private set; } public double CalculateInterestRate() { if (CreditScore > 800) return 0.02; if (AccountAge > 10) return 0.03; return 0.05; } } public class AccountInterest { public BankAccount Account { get; private set; } public AccountInterest(BankAccount account) { Account = account; } public double InterestRate { get { return Account.CalculateInterestRate(); } } public bool IntroductoryRate { get { return Account.CalculateInterestRate() < 0.05; } } } } BankAccount CalculateInterestRate namespace LosTechies.DaysOfRefactoring.MoveMethod.After { public class AccountInterest { public BankAccount Account { get; private set; } public AccountInterest(BankAccount account) { Account = account; } public double InterestRate { get { return CalculateInterestRate(); } } public bool IntroductoryRate { get { return CalculateInterestRate() < 0.05; } } public double CalculateInterestRate() { if (Account.CreditScore > 800) return 0.02; if (Account.AccountAge > 10) return 0.03; return 0.05; } } } namespace LosTechies.DaysOfRefactoring.MoveMethod.After { public class BankAccount { public BankAccount(int accountAge, int creditScore, AccountInterest accountInterest) { AccountAge = accountAge; CreditScore = creditScore; AccountInterest = accountInterest; } public int AccountAge { get; private set; } public int CreditScore { get; private set; } public AccountInterest AccountInterest { get; private set; } } } 3. Turn Car Motorcycle Vehicle namespace LosTechies.DaysOfRefactoring.PullUpMethod.Before { public abstract class Vehicle { // other methods 5 // other methods } public class Car : Vehicle { public void Turn(Direction direction) { // code here } } public class Motorcycle : Vehicle { } public enum Direction { Left, Right } } Car Motorcycle Turn namespace LosTechies.DaysOfRefactoring.PullUpMethod.After { public abstract class Vehicle { public void Turn(Direction direction) { // code here } } public class Car : Vehicle { } public class Motorcycle : Vehicle { } public enum Direction { Left, Right } } 4. Animal Bark Dog Dog namespace LosTechies.DaysOfRefactoring.PushDownMethod.Before { public abstract class Animal { public void Bark() { // code to bark } } public class Dog : Animal { } public class Cat : Animal { } } Animal Bark Animal namespace LosTechies.DaysOfRefactoring.PushDownMethod.After { public abstract class Animal { } public class Dog : Animal { public void Bark() { // code to bark } } public class Cat : Animal { } } 5. 6 Account CheckingAccount SavingsAccount minimumCheckingBalance using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace LosTechies.DaysOfRefactoring.PullUpField.Before { public abstract class Account { } public class CheckingAccount : Account { private decimal _minimumCheckingBalance = 5m; } public class SavingsAccount : Account { private decimal _minimumSavingsBalance = 5m; } } using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace LosTechies.DaysOfRefactoring.PullUpField.After { public abstract class Account { protected decimal _minimumBalance = 5m; } public class CheckingAccount : Account { } public class SavingsAccount : Account { } } 6. Task _resolution BugTask BugTask namespace LosTechies.DaysOfRefactoring.PushDownField.Before { public abstract class Task { protected string _resolution; } public class BugTask : Task { } public class FeatureTask : Task { } } namespace LosTechies.DaysOfRefactoring.PushDownField.After { public abstract class Task { } public class BugTask : Task { private string _resolution; } public class FeatureTask : Task { } } 7. namespace LosTechies.DaysOfRefactoring.Rename.Before { public class Person { public string FN { get; set; } public decimal ClcHrlyPR() { // code to calculate hourly payrate return 0m; 7 return 0m; } } } namespace LosTechies.DaysOfRefactoring.Rename.After { // Changed the class name to Employee public class Employee { public string FirstName { get; set; } public decimal CalculateHourlyPay() { // code to calculate hourly payrate return 0m; } } } 8. Child Sanitation namespace LosTechies.DaysOfRefactoring.ReplaceInheritance.Before { public class Sanitation { public string WashHands() { return "Cleaned!"; } } public class Child : Sanitation { } } Sanitation Child WashHands IOC namespace LosTechies.DaysOfRefactoring.ReplaceInheritance.After { public class Sanitation { public string WashHands() { return "Cleaned!"; } } public class Child { private Sanitation Sanitation { get; set; } public Child() { Sanitation = new Sanitation(); } public string WashHands() { return Sanitation.WashHands(); } } } 9. RegistrationProcessor ClassRegistration Create Total RegistrationProcessor namespace LosTechies.DaysOfRefactoring.ExtractInterface.Before { public class ClassRegistration { public void Create() { // create registration code } public void Transfer() { // class transfer code } public decimal Total { get; private set; } } public class RegistrationProcessor { 8 { public decimal ProcessRegistration(ClassRegistration registration) { registration.Create(); return registration.Total; } } } IClassRegistration ClassRegistration RegistrationProcessor IClassRegistration namespace LosTechies.DaysOfRefactoring.ExtractInterface.After { public interface IClassRegistration { void Create(); decimal Total { get; } } public class ClassRegistration : IClassRegistration { public void Create() { // create registration code } public void Transfer() { // class transfer code } public decimal Total { get; private set; } } public class RegistrationProcessor { public decimal ProcessRegistration(IClassRegistration registration) { registration.Create(); return registration.Total; } } } 10. CalculateGrandTotal subTotal subTotal discount Discounts Tax using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.ExtractMethod.Before { public class Receipt { private IList Discounts { get; set; } private IList ItemTotals { get; set; } public decimal CalculateGrandTotal() { decimal subTotal = 0m; foreach (decimal itemTotal in ItemTotals) subTotal += itemTotal; if (Discounts.Count > 0) { foreach (decimal discount in Discounts) subTotal -= discount; } decimal tax = subTotal * 0.065m; subTotal += tax; return subTotal; } } } CalculateGrandTotal CalculateSubTotal CalculateDiscounts CalculateTax using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.ExtractMethod.After { public class Receipt { private IList Discounts { get; set; } private IList ItemTotals { get; set; } public decimal CalculateGrandTotal() { decimal subTotal = CalculateSubTotal(); subTotal = CalculateDiscounts(subTotal); subTotal = CalculateTax(subTotal); 9 subTotal = CalculateTax(subTotal); return subTotal; } private decimal CalculateTax(decimal subTotal) { decimal tax = subTotal * 0.065m; subTotal += tax; return subTotal; } private decimal CalculateDiscounts(decimal subTotal) { if (Discounts.Count > 0) { foreach (decimal discount in Discounts) subTotal -= discount; } return subTotal; } private decimal CalculateSubTotal() { decimal subTotal = 0m; foreach (decimal itemTotal in ItemTotals) subTotal += itemTotal; return subTotal; } } } 11. switch case if else ClientCode State ShippingInfo namespace LosTechies.DaysOfRefactoring.SwitchToStrategy.Before { public class ClientCode { public decimal CalculateShipping() { ShippingInfo shippingInfo = new ShippingInfo(); return shippingInfo.CalculateShippingAmount(State.Alaska); } } public enum State { Alaska, NewYork, Florida } public class ShippingInfo { public decimal CalculateShippingAmount(State shipToState) { switch (shipToState) { case State.Alaska: return GetAlaskaShippingAmount(); case State.NewYork: return GetNewYorkShippingAmount(); case State.Florida: return GetFloridaShippingAmount(); default: return 0m; } } private decimal GetAlaskaShippingAmount() { return 15m; } private decimal GetNewYorkShippingAmount() { return 10m; } private decimal GetFloridaShippingAmount() { return 3m; } } } IShippingCalculation ShippingInfo GetAlaskaShippingAmount GetNewYorkShippingAmount 10 GetFloridaShippingAmount IShippingCalculation IEnumerable switch case IOC using System; using System.Collections.Generic; using System.Linq; namespace LosTechies.DaysOfRefactoring.SwitchToStrategy.After_WithIoC { public interface IShippingInfo { decimal CalculateShippingAmount(State state); } public class ClientCode { [Inject] public IShippingInfo ShippingInfo { get; set; } public decimal CalculateShipping() { return ShippingInfo.CalculateShippingAmount(State.Alaska); } } public enum State { Alaska, NewYork, Florida } public class ShippingInfo : IShippingInfo { private IDictionary ShippingCalculations { get; set; } public ShippingInfo(IEnumerable shippingCalculations) { ShippingCalculations = shippingCalculations.ToDictionary(calc => calc.State); } public decimal CalculateShippingAmount(State shipToState) { return ShippingCalculations[shipToState].Calculate(); } } public interface IShippingCalculation { State State { get; } decimal Calculate(); } public class AlaskShippingCalculation : IShippingCalculation { public State State { get { return State.Alaska; } } public decimal Calculate() { return 15m; } } public class NewYorkShippingCalculation : IShippingCalculation { public State State { get { return State.NewYork; } } public decimal Calculate() { return 10m; } } public class FloridaShippingCalculation : IShippingCalculation { public State State { get { return State.Florida; } } public decimal Calculate() { return 3m; } } } 12. mock namespace LosTechies.DaysOfRefactoring.BreakDependencies.Before { public class AnimalFeedingService 11 public class AnimalFeedingService { private bool FoodBowlEmpty { get; set; } public void Feed() { if (FoodBowlEmpty) Feeder.ReplenishFood(); // more code to feed the animal } } public static class Feeder { public static void ReplenishFood() { // fill up bowl } } } mock IFeederService AnimalFeedingService namespace LosTechies.DaysOfRefactoring.BreakDependencies.After { public class AnimalFeedingService { public IFeederService FeederService { get; set; } public AnimalFeedingService(IFeederService feederService) { FeederService = feederService; } private bool FoodBowlEmpty { get; set; } public void Feed() { if (FoodBowlEmpty) FeederService.ReplenishFood(); // more code to feed the animal } } public interface IFeederService { void ReplenishFood(); } public class FeederService : IFeederService { public void ReplenishFood() { Feeder.ReplenishFood(); } } public static class Feeder { public static void ReplenishFood() { // fill up bowl } } } 13. Order Calculate using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.ExtractMethodObject.Before { public class OrderLineItem { public decimal Price { get; private set; } } public class Order { private IList OrderLineItems { get; set; } private IList Discounts { get; set; } private decimal Tax { get; set; } public decimal Calculate() { decimal subTotal = 0m; // Total up line items foreach (OrderLineItem lineItem in OrderLineItems) { subTotal += lineItem.Price; } // Subtract Discounts foreach (decimal discount in Discounts) subTotal -= discount; 12 // Calculate Tax decimal tax = subTotal * Tax; // Calculate GrandTotal decimal grandTotal = subTotal + tax; return grandTotal; } } } OrderCalculator Order OrderCalculator Calculate using System.Collections.Generic; namespace LosTechies.DaysOfRefactoring.ExtractMethodObject.After { public class OrderLineItem { public decimal Price { get; private set; } } public class Order { public IEnumerable OrderLineItems { get; private set; } public IEnumerable Discounts { get; private set; } public decimal Tax { get; private set; } public decimal Calculate() { return new OrderCalculator(this).Calculate(); } } public class OrderCalculator { private decimal SubTotal { get; set; } private IEnumerable OrderLineItems { get; set; } private IEnumerable Discounts { get; set; } private decimal Tax { get; set; } public OrderCalculator(Order order) { OrderLineItems = order.OrderLineItems; Discounts = order.Discounts; Tax = order.Tax; } public decimal Calculate() { CalculateSubTotal(); SubtractDiscounts(); CalculateTax(); return SubTotal; } private void CalculateSubTotal() { // Total up line items foreach (OrderLineItem lineItem in OrderLineItems) SubTotal += lineItem.Price; } private void SubtractDiscounts() { // Subtract Discounts foreach (decimal discount in Discounts) SubTotal -= discount; } private void CalculateTax() { // Calculate Tax SubTotal += SubTotal * Tax; } } } 14. Video video rental Customer using System.Collections.Generic; using System.Linq; namespace LosTechies.DaysOfRefactoring.BreakResponsibilities.Before { 13 { public class Video { public void PayFee(decimal fee) { } public void RentVideo(Video video, Customer customer) { customer.Videos.Add(video); } public decimal CalculateBalance(Customer customer) { returncustomer.LateFees.Sum(); } } public class Customer { public IList LateFees { get; set; } public IList