Imagine a Play with Many Actors

Think of a big stage play. Each actor has their own role, but they need to interact smoothly so the story makes sense. Behavioral design patterns are like scripts and rules that guide how objects (actors) talk to each other, share responsibilities, and react to situations.

What are Behavioral Design Patterns?

They are coding techniques that focus on communication between objects—how they interact, make decisions, and delegate tasks. Instead of worrying about how things are built (structure) or created (creational), behavioral patterns are about how things behave together.

Why do we need them?

Without patterns, your code is like a messy group project where:

  • Everyone shouts at once (confusing interactions).
  • Some people do too much work, while others do nothing.
  • It’s hard to reuse or maintain the system.

Behavioral patterns bring order, making sure everyone knows their role.

Examples of Behavioral Design Patterns

1. Observer Pattern 👀

Imagine YouTube subscriptions.

  • You (the user) subscribe to a channel.
  • When the channel uploads a video, all subscribers get notified.
  • In code: one object (the subject) notifies many others (observers).

2. Strategy Pattern 🎯

Think about playing a video game with multiple difficulty modes.

  • Easy, Normal, Hard are different strategies.
  • You can switch strategies without changing the entire game.
  • In code: you can swap algorithms or methods depending on the situation.

3. Command Pattern 🕹️

Imagine using a TV remote.

  • Each button (command) tells the TV what to do: turn on, increase volume, change channel.
  • The remote doesn’t care how the TV works inside, it just sends commands.
  • In code: separate the object that issues requests from the one that executes them.

4. Iterator Pattern 🔄

Think about browsing songs on Spotify.

  • You click next to go through the playlist one by one.
  • You don’t care how the playlist is stored, you just move through items easily.
  • In code: provides a way to access items in a collection without knowing its internal details.

In Short

Behavioral patterns = rules for smooth teamwork between objects. They make programs:

  • Easier to maintain
  • Easier to extend
  • Easier to understand

Review Questions

  1. Behavioral design patterns focus on how objects __________ with each other.
  2. The Observer pattern is like a YouTube channel notifying its __________.
  3. The Strategy pattern allows us to switch between different __________ for solving a problem.
  4. In the Command pattern, the remote control sends __________ to the TV.
  5. The Iterator pattern lets us go through items one by one without knowing the __________ details.
  6. Behavioral patterns make programs easier to maintain, extend, and __________.
  7. The Observer pattern has two main parts: the subject and the __________.
  8. The Strategy pattern is useful when we want to choose different __________ at runtime.
  9. In the Command pattern, the sender is separated from the object that __________ the command.
  10. A playlist that lets you move through songs one by one is an example of the __________ pattern.
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