🔧 Adding

Iterator Pattern

Author: raj713335

06 Behavioral Design Patterns/03 Iterator Design Pattern.py

@@ -0,0 +1,120 @@
+from abc import ABC, abstractmethod
+from typing import List
+
+# --------- Profile class (represents a user in the network) ----------
+class Profile:
+    def __init__(self, profile_id: str, name: str, email: str, company: str, friends: List[str]):
+        self.id = profile_id
+        self.name = name
+        self.email = email
+        self.company = company
+        self.friends = friends
+
+    def __repr__(self):
+        return f"{self.name} ({self.email})"
+
+
+# --------- Iterator Interface ----------
+class ProfileIterator(ABC):
+    @abstractmethod
+    def has_more(self) -> bool:
+        pass
+
+    @abstractmethod
+    def get_next(self) -> Profile:
+        pass
+
+
+# --------- Concrete Iterator ----------
+class FacebookIterator(ProfileIterator):
+    def __init__(self, facebook, profile_id: str, type_: str):
+        self.facebook = facebook
+        self.profile_id = profile_id
+        self.type = type_  # "friends" or "coworkers"
+        self.current_position = 0
+        self.cache = []
+        self._lazy_load()
+
+    def _lazy_load(self):
+        profile = self.facebook.find_profile_by_id(self.profile_id)
+        if not profile:
+            return
+
+        if self.type == "friends":
+            self.cache = self.facebook.get_profiles(profile.friends)
+        elif self.type == "coworkers":
+            all_friends = self.facebook.get_profiles(profile.friends)
+            self.cache = [p for p in all_friends if p.company == profile.company]
+
+    def has_more(self) -> bool:
+        return self.current_position < len(self.cache)
+
+    def get_next(self) -> Profile:
+        if self.has_more():
+            profile = self.cache[self.current_position]
+            self.current_position += 1
+            return profile
+        return None
+
+
+# --------- Collection Interface ----------
+class SocialNetwork(ABC):
+    @abstractmethod
+    def create_friends_iterator(self, profile_id: str) -> ProfileIterator:
+        pass
+
+    @abstractmethod
+    def create_coworkers_iterator(self, profile_id: str) -> ProfileIterator:
+        pass
+
+
+# --------- Concrete Collection ----------
+class Facebook(SocialNetwork):
+    def __init__(self, profiles: List[Profile]):
+        self.profiles = {p.id: p for p in profiles}
+
+    def find_profile_by_id(self, profile_id: str) -> Profile:
+        return self.profiles.get(profile_id)
+
+    def get_profiles(self, ids: List[str]) -> List[Profile]:
+        return [self.profiles[id_] for id_ in ids if id_ in self.profiles]
+
+    def create_friends_iterator(self, profile_id: str) -> ProfileIterator:
+        return FacebookIterator(self, profile_id, "friends")
+
+    def create_coworkers_iterator(self, profile_id: str) -> ProfileIterator:
+        return FacebookIterator(self, profile_id, "coworkers")
+
+
+# --------- Client Code (Spammer) ----------
+class SocialSpammer:
+    def send(self, iterator: ProfileIterator, message: str):
+        while iterator.has_more():
+            profile = iterator.get_next()
+            print(f"Sending '{message}' to {profile.email}")
+
+
+# --------- Application Setup ----------
+def main():
+    # Sample Data
+    profiles = [
+        Profile("1", "Alice", "[email protected]", "ABC Corp", ["2", "3"]),
+        Profile("2", "Bob", "[email protected]", "ABC Corp", ["1"]),
+        Profile("3", "Charlie", "[email protected]", "XYZ Ltd", ["1"]),
+        Profile("4", "David", "[email protected]", "ABC Corp", ["1", "2"]),
+    ]
+
+    facebook = Facebook(profiles)
+    spammer = SocialSpammer()
+
+    print("Send spam to friends of Alice:\n")
+    friends_iterator = facebook.create_friends_iterator("1")
+    spammer.send(friends_iterator, "Hi! This is a spam message.")
+
+    print("\nSend spam to coworkers of Alice:\n")
+    coworkers_iterator = facebook.create_coworkers_iterator("1")
+    spammer.send(coworkers_iterator, "Meeting at 3PM today!")
+
+
+if __name__ == "__main__":
+    main()