gistfile1.txt

BankAccount {
  public void Spend(double amount) { ... }
}

/* ---- */
OneClient {
  ...
    bankAccount.Spend(amount);
  ...
}
/* ---- */
OtherClient {
    ...
    bankAccount.Spend(amount);
    ...
}



/* new changes => log expenses that exceed 1000 euros in a text file */

// Refactor step 1
BankAccount {
 
  public BankAccount() { // used by clients in production code
    
  }

  public void Spend(double amount) { // used by clients in production code
    // ...
    if(amount > 1000) {
        LogExpense(amount);
    }
  }
  
  private void LogExpense(amount) { 
  
  }
  
}


// Refactor step 2
BankAccount {
 
  public BankAccount() { // used by clients in production code
    this.expenseLogger =  new NoExpenseLogger();
  }

  public void Spend(double amount) { // used by clients in production code
    // ...
    if(amount > 1000) {
        LogExpense(amount);
    }
  }
  
  private void LogExpense(amount) { 
     this.expenseLogger.Log(amount);
  }
  
}

NoSpendLogger {
  public void Log(amount) {  }
}

// Refactor step 3
BankAccount {
 
  public BankAccount() { // used by clients in production code
    this.expenseLogger =  new NoExpenseLogger();
  }
  
  public BankAccount(SpendLogger expendLogger) { // no used by clients in production code
    this.spendLogger =  expendeLogger;
  }

  public void Spend(double amount) { // used by clients in production code
    // ...
    if(amount > 1000) {
        LogExpense(amount);
    }
  }
  
  private void LogExpense(amount) { 
     this.expenseLogger.Log(amount);
  }
  
}

NoSpendLogger {
  public void Log(amount) {  }
}

Interface SpendLogger {
  void Log(amount) 
}


// Final state: new feture working
BankAccount {
  
  public BankAccount(SpendLogger expendLogger) { // used by clients in production code
    this.spendLogger =  expendeLogger;
  }

  public void Spend(double amount) { // used by clients in production code
    // ...
    if(amount > 1000) {
        this.expenseLogger.Log(amount);
    }
  }
  
}