Refactoring 016 - Building With The Essence

by Maximiliano ContieriSeptember 16th, 2024

Too Long; Didn't Read

Pass essential attributes during object creation to reduce mutability and eliminate getters and setters. Remove setter and getter methods. Update object creation calls to pass all required attributes upfront. Use the following code snippets to help you understand the code. The code is available on Hackernoon.

featured image - Refactoring 016 - Building With The Essence

Building Immutable foundations from the ground

TL;DR: Pass essential attributes during object creation to reduce mutability and eliminate getters and setters.

Problems Addressed

Mutability
Getters
Setters
Unclear object state
Violating the least surprise principle

Steps

Identify essential attributes required for object creation
Create a constructor that accepts all essential attributes
Remove setter and getter methods
Update object creation calls to pass all required attributes upfront

Sample Code

Before

public class CreditCard {
    private String cardNumber;
    private String cardHolderName;
    private String expirationMonthYear;
    private int cvv;

    public CreditCard() {} // Empty Constructor

    public void setCardNumber(String cardNumber) { 
        this.cardNumber = cardNumber; 
    }
    public void setCardHolderName(String cardHolderName) { 
        this.cardHolderName = cardHolderName; 
    }
    public void setExpirationMonthYear(String expirationMonthYear) { 
        this.expirationMonthYear = expirationMonthYear;
    }
    public void setCvv(int cvv) { 
        this.cvv = cvv; 
    }

    public String getCardNumber() { 
        return cardNumber; 
    }
    public String getCardHolderName() {
        return cardHolderName;
    }
    public String getExpirationMonthYear() {
        return expirationMonthYear; 
    }
    public int getCvv() {
        return cvv; 
    }
}

CreditCard card = new CreditCard();
card.setCardNumber("1234-5678-9012-3456");
card.setCardHolderName("Lilywhite Lilith");
card.setExpirationMonthYear("12/25");
card.setCvv(123);

After

public class CreditCard {
    private final String cardNumber;
    private final String cardHolderName;
    private final String expirationMonthYear;
    private final int cvv;

    public CreditCard(String cardNumber,
                      String cardHolderName,
                      String expirationMonthYear,
                      int cvv) {
        // 1. Identify essential attributes for object creation
        // 2. Create a constructor that accepts all essential attributes
        this.cardNumber = cardNumber;
        this.cardHolderName = cardHolderName;
        this.expirationMonthYear = expirationMonthYear;
        this.cvv = cvv;
    }

    // 3. Remove setter and getter methods 
    
    // Find real behavior related to credit card usage
  
}

// 4. Update object creation calls to pass all required attributes upfront
CreditCard card = new CreditCard("1234-5678-9012-3456",
                                 "Lilywhite Lilith", 
                                 "12/25", 
                                 123);