Refactoring Move Method(将方法移至常被调用的class中)

// 重构前代码说明：

//AccountInterest类拥有一个BankAccount的实例，BankAccount.CalculateInterestRate()方法在AccountInterest类中被调用，而此方法也并非和现在其live的类实例存在依赖关系（不一定被调用）


/// <summary>
/// 简单的银行帐号类
/// </summary>
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; }

    /// <summary>
     /// 将被移除的方法，在其live的class中没有被使用（或者说很少被使用），所以考虑移植到使用最多的class中 AccountInterest，
     /// 提高代码的可读性和可维护性：经常用到的class需要读到，用到，改到此方法的代码的机率更高，同样此方法的修改最主要考虑的也是常用到它的类中的相关业务逻辑。
    /// </summary>
    /// <returns></returns>
     public double CalculateInterestRate()
     {
         if (CreditScore > 800)
         return 0.02;

         if (AccountAge > 10)
         return 0.03;

         return 0.05;
     }
 }

/// <summary>
/// 利息
/// </summary>
 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; }
     }
 }

重构就变得很自然了，重构后的代码如下：

/// <summary>
/// 简单的银行帐号类
/// </summary>
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; }
 
 }

/// <summary>
/// 利息
/// </summary>
 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; }
     }
     /// <summary>
     /// 方法存活在被常调用的类中，其逻辑和此类的关系更为密切。
     /// </summary>
     /// <returns></returns>
     public double CalculateInterestRate()
     {
         if (CreditScore > 800)
             return 0.02;

         if (AccountAge > 10)
             return 0.03;

         return 0.05;
     }
 }

可维护性是衡量代码质量重要的标准之一，此重构值得考虑！