Aggregation

Let’s talk about Aggregation in Object-Oriented Programming — but in our simple, Desi style 😄

✨ What is Aggregation?

It’s a type of “has-a” relationship.
Means: One class contains another class, but both can live independently.
Like: A University has Students, but Students can exist without a University too.

🏦 Real-life Bank Example:

class Customer:
    def __init__(self, name):
        self.name = name

class BankAccount:
    def __init__(self, customer, balance):
        self.customer = customer  # Aggregation
        self.balance = balance

    def show_account(self):
        print(f"Account of {self.customer.name}, Balance: {self.balance}")

Usage:

cust = Customer("Maham")
account = BankAccount(cust, 5000)
account.show_account()

Here, BankAccount has a Customer.
But even if you delete account, cust is still there. So both are not tightly dependent.

🔄 Aggregation vs Composition:

Concept	Aggregation	Composition
Dependency	Weak (can exist independently)	Strong (cannot exist separately)
Example	BankAccount has a Customer	Car has an Engine (engine dies with car)

👀 Common Questions:

Q: Is aggregation same as inheritance?
➜ No yaar, inheritance is "is-a", aggregation is "has-a".
Q: Can we access aggregated class properties?
➜ Haan ji! self.customer.name kind of access is common.
Q: What happens if parent is deleted?
➜ Nothing happens to the child in aggregation. It survives.

okay simply a class can be a property in another class right?

Exactly! 💡

Yes, a class can be used as a property inside another class
That’s called a "has-a" relationship (like aggregation or composition)

Example:

class Engine:
    def __init__(self, horsepower):
        self.horsepower = horsepower

class Car:
    def __init__(self, engine):
        self.engine = engine  # Engine is used as a property

    def show(self):
        print(f"Car with {self.engine.horsepower} HP engine")

Output:

e = Engine(120)
c = Car(e)
c.show()

✔️ So yes — class as a property = totally valid and very useful!

Want the composition example next?