Creational patterns are about how objects get created. The basic way to create an object is the new operator. It can cause design problems or add complexity. Creational patterns solve this by controlling how objects are created, so the way fits the situation.
1. Quick Comparison Table
| Pattern | Primary Focus | Key Mechanism | Best For... |
|---|---|---|---|
| Singleton | Identity | One shared instance, and one way to reach it. | Shared resources (Loggers, DB pools). |
| Factory | Choice | A factory creates one object for you. | When you have one interface with many implementations (Logistics). |
| Abstract Factory | Families | Creating groups of related objects together. | Regional requirements (Payment + Invoice). |
| Builder | Step-by-Step | Building a complex object part by part. | Objects with many optional fields (BurgerMeal). |
| Prototype | Copying | Cloning an object that is already set up. | Heavy initialization cost (Email Templates). |
2. When to Use vs. When to Avoid
Singleton Pattern
- When to Use: When exactly one instance of a class must coordinate actions across the system (e.g., a central error logger).
- When to Avoid: For general data storage or when you need independent instances for different users. Overusing it makes unit testing hard.
Factory Pattern (Simple Factory and Factory Method)
- When to Use: When a class cannot know in advance which type of object it must create, so a factory decides. In the subclass version (Factory Method), the subclasses decide. The repo example is a Simple Factory.
- When to Avoid: When the number of products is small and unlikely to change, because it adds extra layers of code (abstraction) you do not need.
Abstract Factory Pattern
- When to Use: When your system should not depend on how its products are created, and related products (a "family") must work together.
- When to Avoid: When you only have one family of products, because it needs many interfaces and factory classes.
Builder Pattern
- When to Use: When you need to create an object with a lot of optional parameters or when the same building steps must give different versions of the object.
- When to Avoid: When the object is simple or has only a few required fields. A normal constructor is much faster to write.
Prototype Pattern
- When to Use: When the cost of creating a brand-new instance is high (e.g., database hits or complex parsing) or when you want to keep the number of classes low.
- When to Avoid: When objects are simple to create or when the object's state has circular references (objects pointing at each other) that are hard to deep-clone.
3. The "Rule of Thumb" for Decision Making
- Is it a single global instance? → Singleton.
- Is the creation process "heavy" or repetitive? → Prototype.
- Does the object have 5+ optional configuration parts? → Builder.
- Are you choosing between implementations of one interface? → Factory.
- Are you choosing a whole suite of related tools based on a region/theme? → Abstract Factory.