Classificare i design pattern
Impari a conoscere le tre categorie principali: pattern creazionali, strutturali e comportamentali, e il loro ruolo nell’architettura software.
Classificare i design pattern è una lezione Clean Architecture & Design Patterns in Practice gratuita su CoddyKit. Questa è la lezione 2 di 4. Puoi leggere la lezione completa qui gratuitamente — poi esercitati direttamente nel browser con un editor di codice integrato e un tutor IA disponibile 24/7. Fa parte del percorso di apprendimento Clean Architecture & Design Patterns in Practice, e i tuoi progressi si sincronizzano tra il web e l'app CoddyKit. Il corso Clean Architecture & Design Patterns in Practice include 4 lezioni in totale.
Parti di questa lezione non sono ancora state tradotte e vengono mostrate in inglese.
Organizing Design Patterns
Welcome back! In our last lesson, we learned what design patterns are. Now, let's explore how they are organized.
Just like books in a library, design patterns are grouped into categories. This helps us understand their purpose and when to use them effectively.
The Three Main Categories
Design patterns are traditionally divided into three main categories. Each category addresses a different type of problem in software design:
- Creational Patterns: Deal with object creation.
- Structural Patterns: Focus on object composition and relationships.
- Behavioral Patterns: Concern object interaction and responsibilities.
Let's dive into each one!
Creational Patterns: Object Creation
Creational patterns are all about how objects are created. They aim to provide flexible and controlled ways to instantiate objects, rather than using direct constructors.
This helps make a system independent of how its objects are created, composed, and represented. They make your code more adaptable to change.
Creational Example: Simple Creator
Imagine you need to create different types of reports. A creational pattern might use a method to decide which report type to build, instead of you calling `new` directly.
Try running this simple example:
public class Main {
public static String createReport(String type) {
if ("PDF".equals(type)) {
return "Generating PDF Report...";
} else if ("CSV".equals(type)) {
return "Generating CSV Report...";
}
return "Unknown Report Type.";
}
public static void main(String[] args) {
System.out.println(createReport("PDF"));
System.out.println(createReport("CSV"));
}
}Structural Patterns: Composition
Structural patterns deal with the composition of classes and objects. They help you assemble objects and classes into larger, more flexible structures.
These patterns focus on how objects are related to each other, often by identifying simple ways to realize relationships between entities.
Structural Example: Object Assembly
Structural patterns are like building blocks. They show how to combine objects to form new functionalities. Think of a computer having a CPU and RAM.
Run this code to see a simple composition:
public class Main {
static class CPU {
String process() { return "CPU processing..."; }
}
static class Computer {
private CPU cpu; // Computer HAS-A CPU (composition)
public Computer() {
this.cpu = new CPU();
}
public String start() {
return cpu.process() + " Computer booting up.";
}
}
public static void main(String[] args) {
Computer myPC = new Computer();
System.out.println(myPC.start());
}
}Behavioral Patterns: Object Interaction
Behavioral patterns are concerned with algorithms and the assignment of responsibilities between objects. They describe how objects communicate and interact with each other.
These patterns help ensure that objects can work together efficiently and flexibly, managing complex processes and interactions.
Behavioral Example: Simple Action
Behavioral patterns often define how an action is performed or how objects respond to requests. Here's a simple example of a light switching on and off:
Run the code to see the light's behavior:
public class Main {
static class Light {
private boolean isOn = false;
public String toggle() {
isOn = !isOn;
if (isOn) {
return "Light is now ON.";
} else {
return "Light is now OFF.";
}
}
}
public static void main(String[] args) {
Light livingRoomLight = new Light();
System.out.println(livingRoomLight.toggle()); // First toggle
System.out.println(livingRoomLight.toggle()); // Second toggle
}
}Why Categorize Patterns?
Categorizing design patterns helps you in several ways:
- Easier Search: If you know you need to solve an object creation problem, you can focus on Creational patterns.
- Better Understanding: It clarifies the primary purpose and scope of a pattern.
- Improved Communication: Teams can discuss patterns using a common language based on their categories.
It's a powerful tool for navigating the world of design patterns!
Categorization Check
Which category of design patterns primarily focuses on how objects are put together to form larger structures?
Recap: The Pattern Categories
Great job! In this lesson, we explored the three main categories of design patterns:
- Creational: For flexible object creation.
- Structural: For building larger, more flexible object compositions.
- Behavioral: For managing object interactions and responsibilities.
Understanding these categories is your first step to mastering design patterns. Next, we'll see how these patterns appear in everyday coding!
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Tutte le lezioni di questo corso
- Cosa sono i design pattern?
- Classificare i design pattern
- I pattern nella programmazione quotidiana
- Anti-pattern e costi dell'uso improprio dei pattern