Flask大型教程:关注者，联系人和好友

Post.query.join(followers,
    (followers.c.followed_id == Post.user_id))

filter(followers.c.follower_id == self.id)

order_by(Post.timestamp.desc())

#...
from datetime import datetime, timedelta
from app.models import User, Post
#...
class TestCase(unittest.TestCase):
    #...
    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]

@oid.after_login
def after_login(resp):
    if resp.email is None or resp.email == "":
        flash('Invalid login. Please try again.')
        redirect(url_for('login'))
    user = User.query.filter_by(email = resp.email).first()
    if user is None:
        nickname = resp.nickname
        if nickname is None or nickname == "":
            nickname = resp.email.split('@')[0]
        nickname = User.make_unique_nickname(nickname)
        user = User(nickname = nickname, email = resp.email)
        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']
        session.pop('remember_me', None)
    login_user(user, remember = remember_me)
    return redirect(request.args.get('next') or url_for('index'))

@app.route('/follow/<nickname>')
@login_required
def follow(nickname):
    user = User.query.filter_by(nickname=nickname).first()
    if user is None:
        flash('User %s not found.' % nickname)
        return redirect(url_for('index'))
    if user == g.user:
        flash('You can\'t follow yourself!')
        return redirect(url_for('user', nickname=nickname))
    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>')
@login_required
def unfollow(nickname):
    user = User.query.filter_by(nickname=nickname).first()
    if user is None:
        flash('User %s not found.' % nickname)
        return redirect(url_for('index'))
    if user == g.user:
        flash('You can\'t unfollow yourself!')
        return redirect(url_for('user', nickname=nickname))
    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))

<!-- extend base layout -->
{% extends "base.html" %}

{% block content %}
<table>
    <tr valign="top">
        <td><img src="{{user.avatar(128)}}"></td>
        <td>
            <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 %}
            <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>
<hr>
{% for post in posts %}
    {% include 'post.html' %}
{% endfor %}
{% endblock %}