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🔧 Adding
Observer Pattern
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‎06 Behavioral Design Patterns/06 Observer Design Pattern.py‎

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from abc import ABC, abstractmethod
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from typing import List
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# Observer Interface
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class Subscriber(ABC):
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@abstractmethod
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def update(self, product_name: str):
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...
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# Concreate Observers
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class EmailCustomer(Subscriber):
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def __init__(self, name: str, email: str):
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self.name = name
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self.email = email
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def update(self, product_name: str):
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print(f"[Email] To: {self.email} | {self.name}, the product '{product_name}' is now available.")
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class SMSCustomer(Subscriber):
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def __init__(self, name: str, phone: str):
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self.name = name
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self.phone = phone
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def update(self, product_name: str):
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print(f"[SMS] To: {self.phone} | {self.name}, the product '{product_name}' is available.")
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# PUBLISHER Class
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class Store:
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def __init__(self, store_name: str):
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self.store_name = store_name
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self._subscribers: List[Subscriber] = []
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def subscribe(self, subscriber: Subscriber):
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self._subscribers.append(subscriber)
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print(f"{subscriber.__class__.__name__} subscribed to {self.store_name}")
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def unscribe(self, subscriber: Subscriber):
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self._subscribers.remove(subscriber)
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print(f"{subscriber.__class__.__name__} unsubscribed from {self.store_name}")
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def notify_subscriber(self, product_name: str):
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print(f"\n[{self.store_name}] Notifying all subscriber about: {product_name}")
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for subscriber in self._subscribers:
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subscriber.update(product_name)
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def add_new_product(self, product_name: str):
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print(f"\n[{self.store_name}] New Product added: {product_name}")
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self.notify_subscriber(product_name)
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# Client Code
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if __name__ == "__main__":
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# Create a store (Publisher)
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apple_store = Store("Apple Store")
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# Create customers (Subscribers)
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john = EmailCustomer("John Doe", "[email protected]")
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jane = SMSCustomer("Jane Doe", "+1288488483")
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# Subscriptions
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apple_store.subscribe(john)
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apple_store.subscribe(jane)
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# Store adds a product
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apple_store.add_new_product("Iphone 20 Max Pro")
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# Unsubscribe Jane
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apple_store.unscribe(jane)
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# Add another product
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apple_store.add_new_product("Mac Book Air 20 Plus")

‎Data/Pro Vs Cons.html‎

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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Prototype Design Pattern: Pros vs. Cons</title>
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<title>Visitor Design Pattern: Pros vs. Cons</title>
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<!-- Google Fonts: Inter -->
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<link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;600;700&display=swap" rel="stylesheet">
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<!-- Tailwind CSS CDN -->
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<div class="container mx-auto bg-white shadow-2xl overflow-hidden max-w-6xl w-full">
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<!-- Header Section -->
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<div class="bg-gradient-to-r from-teal-600 to-cyan-700 text-white p-6 md:p-8 text-center">
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<div class="bg-gradient-to-r from-green-700 to-lime-600 text-white p-6 md:p-8 text-center">
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<h1 class="text-3xl md:text-5xl font-extrabold mb-2 leading-tight">
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<span class="block text-amber-300 mb-2"><i class="fa-solid fa-robot"></i></span> Prototype Design Pattern: Pros vs. Cons
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<span class="block text-amber-300 mb-2"><i class="fa-solid fa-person-walking"></i></span> Visitor Design Pattern: Pros vs. Cons
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</h1>
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<p class="text-lg md:text-xl font-light opacity-90">Creating Families of Related Objects</p>
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<p class="text-lg md:text-xl font-light opacity-90">Adding New Operations to Existing Object Structures Without Modifying Them</p>
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</div>
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<!-- Main Content: Pros and Cons Columns -->
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.707 9.293a1 1 0 00-1.414 1.414l2 2a1 1 0 001.414 0l4-4z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Reduces the need for subclassing:</span> You can create new objects by copying existing ones, avoiding the need for many subclasses.
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<span class="font-bold">Open/Closed Principle:</span> New operations can be added without modifying the existing object structure.
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</div>
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</li>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-green-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.707 9.293a1 1 0 00-1.414 1.414l2 2a1 1 0 001.414 0l4-4z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Hides the complexity of object creation:</span> Clients can clone objects without knowing the details of their construction.
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<span class="font-bold">Separation of concerns:</span> Operations are separated from the objects on which they operate, improving maintainability.
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</div>
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</li>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-green-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.707 9.293a1 1 0 00-1.414 1.414l2 2a1 1 0 001.414 0l4-4z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Speeds up the instantiation of complex objects:</span> Cloning is often faster than constructing a new object from scratch, especially for resource-intensive objects.
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<span class="font-bold">Easier to add new behaviors:</span> New visitor classes can be created to add new behaviors without changing existing code.
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</div>
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</li>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-green-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.707 9.293a1 1 0 00-1.414 1.414l2 2a1 1 0 001.414 0l4-4z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Allows adding and removing objects at runtime:</span> New prototypes can be registered and cloned as needed, providing flexibility.
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<span class="font-bold">Supports operations across class hierarchies:</span> Can perform operations on a set of objects with different concrete classes.
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</div>
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</li>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-green-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.707 9.293a1 1 0 00-1.414 1.414l2 2a1 1 0 001.414 0l4-4z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Useful for objects that are expensive to create:</span> Especially when object creation involves a costly setup or configuration process.
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<span class="font-bold">Facilitates adding features:</span> Useful for adding features like traversals, reporting, or exporting without modifying the object structure.
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</div>
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</li>
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</ul>
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Cloning complex objects with circular references can be tricky:</span> Special care is needed to avoid infinite loops or errors during cloning.
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<span class="font-bold">Breaks encapsulation:</span> The visitor may need to access internal details of elements, breaking encapsulation.
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</div>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-red-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Requires implementing a cloning method for each prototype:</span> Every class that needs to be cloned must provide its own cloning logic.
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<span class="font-bold">Difficult to add new element types:</span> Adding new element classes requires updating all existing visitors.
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</div>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-red-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Deep copy vs. shallow copy issues can arise:</span> Care must be taken to ensure the correct type of copy is made, especially for objects with references to other objects.
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<span class="font-bold">Complex double-dispatch:</span> Requires double-dispatch, which can make the code harder to follow and maintain.
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</div>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-red-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Not always clear when to use:</span> Sometimes using constructors or factory methods is simpler and more appropriate than cloning.
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<span class="font-bold">Can be overkill for simple structures:</span> Adds unnecessary complexity if only a few operations are needed.
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</div>
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</li>
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<li class="flex items-start">
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<span class="flex-shrink-0 text-red-500 mt-1 mr-3">
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<svg class="w-6 h-6" fill="currentColor" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clip-rule="evenodd"></path></svg>
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</span>
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<div class="flex-1">
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<span class="font-bold">Visitor pattern can break encapsulation:</span> The visitor may require access to the internal state of elements, which can break encapsulation.
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</div>
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</li>
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</ul>

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