Today we're going to build a clone of a social network (really similar to the blue bird one, but keep it a secret).

As any other social network we're going to have different types of Posts. All these different types of Posts should inherit from the parent Post class:

• TextPost: Just a simple text post. Should be constructed as TextPost(text="Post Text").
• PicturePost: A post containing text and the URL of a picture: Should be constructed as PicturePost(text="Post Text", image_url="imgur.com/OAWTSJu").
• CheckInPost: A post containing text and coordinates of the user's position. Should be constructed as CheckInPost(text="Post Text", latitude="40.741895", longitude="-73.989308").

Rmotrgram also has users. A user is a simple class that can be created as: User(first_name="John", last_name="Smith", email="[email protected]").

Posts are going to be created and then assigned a user. Once we have our user and post created, we're going to use the add_post method from the user class. add_post should add the post to the user's list of posts, and assign that user to the post. Example, to create a text post for our user John, we'll do something like:

john = User("John", "Lennon", "[email protected]")
text_post = TextPost("All you need is love!")
text_post.user == None  # Important! Since the post has no user yet, the user attribute should be None.

john.add_post(text_post)

text_post.user == john  # Important!
len(john.posts)
>>> 1

As you can see from our previous example, a post is created without a user. It's an "orphan" we might say. By default when a post is created it's user attribute is None. But once we add that post to a user using add_post(), the post's user attribute should be updated, and the post should be added to the user's list of posts.

Users will be able to follow other users. The follow method is super simple:

john = User("John", "Lennon", "[email protected]")
paul = User("Paul", "McCartney", "[email protected]")

john.follow(paul)
print(john.following)
>>> [<User: "Paul McCartney">]

This should be almost exactly like twitter. A user will have a timeline, that's just a list of posts created by other users that we're following, sorted by datetime (most recent first).

john = User("John", "Lennon", "[email protected]")
paul = User("Paul", "McCartney", "[email protected]")
george = User("George", "Harrison", "[email protected]")

john.follow(paul)
john.follow(george)

paul.add_post(TextPost("Post 1"))
george.add_post(TextPost("Post 2"))
paul.add_post(TextPost("Post 3"))

print(john.following)
>>>[[<User: "Paul McCartney">], [<User: "George Harrison">]] # John is following Paul and George

print(john.get_timeline())
>>> [<TextPost: Post 3>, <TextPost: Post 2>, <TextPost: Post 1> 

Important: A user's timeline should only include posts from the users they are following.

Finally, one of the most interesting use cases of this project is going to be realted to the "visual representation" of the posts. It's a great example of Polymorphism. The concept is simple. If I try to print different types of posts, I'm going to get different representations. Example:

john = User("John", "Lennon", "[email protected]")
text_post_1 = TextPost("All you need is love!")
picture_post_2 = PicturePost("Check my new submarine.", image_url='imgur.com/submarine.jpg')
checkin_post_3 = CheckInPost("At Abbey Road Studios", latitude="19.111", longitude="-9.2222")
john.add_post(text_post_1)
john.add_post(picture_post_2)
john.add_post(checkin_post_3)

print(text_post_1)
"""
John Lennon: "All you need is love!"
  Friday, Feb 03, 2017
"""

print(picture_post_2)
"""
John Lennon: "Check my new guitar"
  Pic URL: imgur.com/guitar.png
  Friday, Feb 03, 2017
"""

print(checkin_post_3)
"""
John Checked In: "At Abbey Road Studios"
  19.111, -9.2222
  Friday, Feb 03, 2017
"""

(check tests to see more examples)