Behavioral patterns (Observer, Strategy, Command) in Software Engineering - Mini Project: Build & Apply

Understanding Behavioral Patterns: Observer, Strategy, and Command

📖 Scenario: You are building a simple notification system for a weather app. The app needs to notify different parts of the system when the weather changes, allow users to choose different ways to get weather updates, and execute commands like turning notifications on or off.

🎯 Goal: Build a basic structure demonstrating the Observer, Strategy, and Command behavioral patterns using simple code examples and explanations.

📋 What You'll Learn

Create a list of observers representing parts of the system to be notified

Define a strategy variable to select the notification method

Implement a command structure to turn notifications on or off

Combine these patterns to simulate a weather update notification

💡 Why This Matters

🌍 Real World

Behavioral patterns like Observer, Strategy, and Command help organize code in apps that need flexible communication, different behaviors, and controlled actions, such as weather apps, messaging systems, or user interfaces.

💼 Career

Understanding these patterns is important for software developers to write clean, maintainable, and scalable code that adapts to changing requirements.

1

Set up the list of observers

Create a list called observers with these exact string entries: 'Display', 'Logger', and 'MobileApp' representing parts of the system that will receive weather updates.

Software Engineering

# Create a list called observers with 'Display', 'Logger', and 'MobileApp'
# Your code here

Hint

Use square brackets to create a list and separate items with commas.

2

Add a strategy variable for notification method

Create a variable called notification_method and set it to the string 'Email' to represent the chosen way to send weather updates.

Software Engineering

observers = ['Display', 'Logger', 'MobileApp']
# Create a variable notification_method and set it to 'Email'
# Your code here

Hint

Assign the string 'Email' directly to the variable notification_method.

3

Implement a command to toggle notifications

Create a variable called notifications_on and set it to True to represent that notifications are currently enabled.

Software Engineering

observers = ['Display', 'Logger', 'MobileApp']
notification_method = 'Email'
# Create a variable notifications_on and set it to True
# Your code here

Hint

Use the boolean value True to indicate notifications are enabled.

4

Combine patterns to simulate a weather update

Write a for loop using observer as the variable to iterate over observers. Inside the loop, write a comment that says # Notify {observer} via {notification_method}. Then add an if statement that checks if notifications_on is True and write a comment inside it that says # Send update.

Software Engineering

observers = ['Display', 'Logger', 'MobileApp']
notification_method = 'Email'
notifications_on = True
# Use a for loop to notify each observer
# Your code here

Hint

Use a for loop with the variable observer to go through observers. Use an if statement to check notifications_on.