followers

app/models.py

@@ -4,6 +4,11 @@ from app import db
 ROLE_USER = 0
 ROLE_ADMIN = 1
 
+followers = db.Table('followers',
+    db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
+    db.Column('followed_id', db.Integer, db.ForeignKey('user.id'))
+)
+
 class User(db.Model):
     id = db.Column(db.Integer, primary_key = True)
     nickname = db.Column(db.String(64), unique = True)
@@ -12,6 +17,12 @@ class User(db.Model):
     posts = db.relationship('Post', backref = 'author', lazy = 'dynamic')
     about_me = db.Column(db.String(140))
     last_seen = db.Column(db.DateTime)
+    followed = db.relationship('User', 
+        secondary = followers, 
+        primaryjoin = (followers.c.follower_id == id), 
+        secondaryjoin = (followers.c.followed_id == id), 
+        backref = db.backref('followers', lazy = 'dynamic'), 
+        lazy = 'dynamic')
 
     @staticmethod
     def make_unique_nickname(nickname):
@@ -40,6 +51,22 @@ class User(db.Model):
     def avatar(self, size):
         return 'http://www.gravatar.com/avatar/' + md5(self.email).hexdigest() + '?d=mm&s=' + str(size)
         
+    def follow(self, user):
+        if not self.is_following(user):
+            self.followed.append(user)
+            return self
+            
+    def unfollow(self, user):
+        if self.is_following(user):
+            self.followed.remove(user)
+            return self
+            
+    def is_following(self, user):
+        return self.followed.filter(followers.c.followed_id == user.id).count() > 0
+
+    def followed_posts(self):
+        return Post.query.join(followers, (followers.c.followed_id == Post.user_id)).filter(followers.c.follower_id == self.id).order_by(Post.timestamp.desc())
+        
     def __repr__(self):
         return '<User %r>' % (self.nickname)    
         

app/templates/user.html

@@ -9,7 +9,15 @@
             <h1>User: {{user.nickname}}</h1>
             {% if user.about_me %}<p>{{user.about_me}}</p>{% endif %}
             {% if user.last_seen %}<p><i>Last seen on: {{user.last_seen}}</i></p>{% endif %}
-            {% if user.id == g.user.id %}<p><a href="{{url_for('edit')}}">Edit</a></p>{% endif %}
+            <p>{{user.followers.count()}} followers | 
+            {% if user.id == g.user.id %}
+                <a href="{{url_for('edit')}}">Edit your profile</a>
+            {% elif not g.user.is_following(user) %}
+                <a href="{{url_for('follow', nickname = user.nickname)}}">Follow</a>
+            {% else %}
+                <a href="{{url_for('unfollow', nickname = user.nickname)}}">Unfollow</a>
+            {% endif %}
+            </p>
         </td>
     </tr>
 </table>

app/views.py

@@ -73,6 +73,9 @@ def after_login(resp):
         user = User(nickname = nickname, email = resp.email, role = ROLE_USER)
         db.session.add(user)
         db.session.commit()
+        # make the user follow him/herself
+        db.session.add(user.follow(user))
+        db.session.commit()
     remember_me = False
     if 'remember_me' in session:
         remember_me = session['remember_me']
@@ -117,3 +120,32 @@ def edit():
     return render_template('edit.html',
         form = form)
 
+@app.route('/follow/<nickname>')
+def follow(nickname):
+    user = User.query.filter_by(nickname = nickname).first()
+    if user == None:
+        flash('User ' + nickname + ' not found.')
+        return redirect(url_for('index'))
+    u = g.user.follow(user)
+    if u is None:
+        flash('Cannot follow ' + nickname + '.')
+        return redirect(url_for('user', nickname = nickname))
+    db.session.add(u)
+    db.session.commit()
+    flash('You are now following ' + nickname + '!')
+    return redirect(url_for('user', nickname = nickname))
+
+@app.route('/unfollow/<nickname>')
+def unfollow(nickname):
+    user = User.query.filter_by(nickname = nickname).first()
+    if user == None:
+        flash('User ' + nickname + ' not found.')
+        return redirect(url_for('index'))
+    u = g.user.unfollow(user)
+    if u is None:
+        flash('Cannot unfollow ' + nickname + '.')
+        return redirect(url_for('user', nickname = nickname))
+    db.session.add(u)
+    db.session.commit()
+    flash('You have stopped following ' + nickname + '.')
+    return redirect(url_for('user', nickname = nickname))

db_repository/versions/004_migration.py

@@ -0,0 +1,26 @@
+from sqlalchemy import *
+from migrate import *
+
+
+from migrate.changeset import schema
+pre_meta = MetaData()
+post_meta = MetaData()
+followers = Table('followers', post_meta,
+    Column('follower_id', Integer),
+    Column('followed_id', Integer),
+)
+
+
+def upgrade(migrate_engine):
+    # Upgrade operations go here. Don't create your own engine; bind
+    # migrate_engine to your metadata
+    pre_meta.bind = migrate_engine
+    post_meta.bind = migrate_engine
+    post_meta.tables['followers'].create()
+
+
+def downgrade(migrate_engine):
+    # Operations to reverse the above upgrade go here.
+    pre_meta.bind = migrate_engine
+    post_meta.bind = migrate_engine
+    post_meta.tables['followers'].drop()

tests.py

@@ -1,10 +1,11 @@
 #!flask/bin/python
 import os
 import unittest
+from datetime import datetime, timedelta
 
 from config import basedir
 from app import app, db
-from app.models import User
+from app.models import User, Post
 
 class TestCase(unittest.TestCase):
     def setUp(self):
@@ -14,6 +15,7 @@ class TestCase(unittest.TestCase):
         db.create_all()
         
     def tearDown(self):
+        db.session.remove()
         db.drop_all()
 
     def test_avatar(self):
@@ -38,5 +40,78 @@ class TestCase(unittest.TestCase):
         assert nickname2 != 'john'
         assert nickname2 != nickname
         
+    def test_follow(self):
+        u1 = User(nickname = 'john', email = 'john@example.com')
+        u2 = User(nickname = 'susan', email = 'susan@example.com')
+        db.session.add(u1)
+        db.session.add(u2)
+        db.session.commit()
+        assert u1.unfollow(u2) == None
+        u = u1.follow(u2)
+        db.session.add(u)
+        db.session.commit()
+        assert u1.follow(u2) == None
+        assert u1.is_following(u2)
+        assert u1.followed.count() == 1
+        assert u1.followed.first().nickname == 'susan'
+        assert u2.followers.count() == 1
+        assert u2.followers.first().nickname == 'john'
+        u = u1.unfollow(u2)
+        assert u != None
+        db.session.add(u)
+        db.session.commit()
+        assert u1.is_following(u2) == False
+        assert u1.followed.count() == 0
+        assert u2.followers.count() == 0
+        
+        def test_follow_posts(self):
+            # make four users
+            u1 = User(nickname = 'john', email = 'john@example.com')
+            u2 = User(nickname = 'susan', email = 'susan@example.com')
+            u3 = User(nickname = 'mary', email = 'mary@example.com')
+            u4 = User(nickname = 'david', email = 'david@example.com')
+            db.session.add(u1)
+            db.session.add(u2)
+            db.session.add(u3)
+            db.session.add(u4)
+            # make four posts
+            utcnow = datetime.utcnow()
+            p1 = Post(body = "post from john", author = u1, timestamp = utcnow + timedelta(seconds = 1))
+            p2 = Post(body = "post from susan", author = u2, timestamp = utcnow + timedelta(seconds = 2))
+            p3 = Post(body = "post from mary", author = u3, timestamp = utcnow + timedelta(seconds = 3))
+            p4 = Post(body = "post from david", author = u4, timestamp = utcnow + timedelta(seconds = 4))
+            db.session.add(p1)
+            db.session.add(p2)
+            db.session.add(p3)
+            db.session.add(p4)
+            db.session.commit()
+            # setup the followers
+            u1.follow(u1) # john follows himself
+            u1.follow(u2) # john follows susan
+            u1.follow(u4) # john follows david
+            u2.follow(u2) # susan follows herself
+            u2.follow(u3) # susan follows mary
+            u3.follow(u3) # mary follows herself
+            u3.follow(u4) # mary follows david
+            u4.follow(u4) # david follows himself
+            db.session.add(u1)
+            db.session.add(u2)
+            db.session.add(u3)
+            db.session.add(u4)
+            db.session.commit()
+            # check the followed posts of each user
+            f1 = u1.followed_posts().all()
+            f2 = u2.followed_posts().all()
+            f3 = u3.followed_posts().all()
+            f4 = u4.followed_posts().all()
+            assert len(f1) == 3
+            assert len(f2) == 2
+            assert len(f3) == 2
+            assert len(f4) == 1
+            assert f1 == [p4, p2, p1]
+            assert f2 == [p3, p2]
+            assert f3 == [p4, p3]
+            assert f4 == [p4]
+        
 if __name__ == '__main__':
     unittest.main()