Chapter 11 Blog Posts
Blog Post Submission and Display
app/models.py中添加Post表
class Post(db.Model):
__tablename__ = 'posts'
id = db.Column(db.Integer, primary_key=True)
body = db.Column(db.Text)
timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
author_id = db.Column(db.Integer, db.ForeignKey('users.id'))
class User(UserMixin, db.Model):
# ...
posts = db.relationship('Post', backref='author', lazy='dynamic')
app/main/forms.py中添加表单
class PostForm(Form):
body = TextAreaField("what's on you mind?", validators=[Required()])
submit = SubmitField('Submit')
app/main/views.py
@main.route('/', methods=['GET', 'POST'])
def index():
form = PostForm()
if current_user.can(Permission.WRITE_ARTICLES) and \
form.validate_on_submit():
post = Post(body=form.body.data,
author=current_user._get_current_object())
db.session.add(post)
return redirect(url_for('.index'))
posts = Post.query.order_by(Post.timestamp.desc()).all()
return render_template('index.html', form=form, posts=posts)
app/templates/index.html
{% extends "base.hmtl" %}
{% import "bootstrap/wtf.hmtl" as wtf %}
<div>
{% if current_user.can(Permission.WRITE_ARTICLES) %}
{{ wtf.quick_form(form) }}
{% endif %}
</div>
<ul class="posts">
{% for post in posts %}
<li class="post">
<div class="profile-thumbnail">
<a href="{{ url_for('.user', username=post.author.username) }}">
<img class="img-rounded profile-thumbnail"
src="{{ post.author.gravatar(size=40) }}">
</a>
</div>
<div class="post-date">{{ moment(post.timestamp).fromNow() }}</div>
<div class="post-author">
<a href="{{ url_for('.user', username=post.author.username) }}">
{{ post.author.username }}
</a>
</div>
<div class="post-body">{{ post.body }}</div>
</li>
{% endfor %}
</ul>
app/main/__init__.py中添加语句
from ..models import Permission
@main.app_context_processor
def inject_permissions():
return dict(Permission=Permission)
在app/manage.py中添加语句
from app.models import Permission, Post
def make_shell_context():
return dict(app=app, db=db, User=User, Role=Role,
Permission=Permission, Post=Post)
更新数据库
python manage.py db migrate -m "postBlog"
python manage.py db upgrade
Blog Posts on Profile Pages
app/main/views.py
@main.route('/user/<username>')
def user(username):
user = User.query.filter_by(username=username).first_or_404()
posts = user.posts.order_by(Post.timestamp.desc()).all()
return render_template('user.html', user=user, posts=posts)
然后在app/templates/user.html中做响应修改。由于其中需要添加的语句和app/templates/index.html
中的完全相同，所以可以提取出来放入单独的一个文件如_posts.html中，然后使用include()语句引用
app/templates/_posts.html
<ul class="posts">
{% for post in posts %}
<li class="post">
<div class="profile-thumbnail">
<a href="{{ url_for('.user', username=post.author.username) }}">
<img class="img-rounded profile-thumbnail"
src="{{ post.author.gravatar(size=40) }}">
</a>
</div>
<div class="post-date">{{ moment(post.timestamp).fromNow() }}</div>
<div class="post-author">
<a href="{{ url_for('.user', username=post.author.username) }}">
{{ post.author.username }}
</a>
</div>
<div class="post-body">{{ post.body }}</div>
</li>
{% endfor %}
</ul>
app/templates/user.html
<h3>Posts by {{ user.username }}</h3>
{% include '_posts.html' %}
app/templates/index.html中也可以做类似的修改
Paginating Long Blog Post Lists
如果博客数量过多则列表显示则很长，则可以考虑分页显示
Creating Fake Blog Post data
为了测试大量数据时的情况，可是使用forgerypy来生成所需的数据
pip install forgerypy
由于forgerypy只在开发测试时需要，所以可以将项目所需依赖相分成dev.txt和prod.txt两个。
而对于两者共有的依赖库可以放在common.txt中，然后在dev.txt和prod.txt中的列表前面添加
-r common.txt来解决
app/models.py中添加生成测试数据的函数
class User(UserMixin, db.Model):
#...
@staticmethod
def generate_fake(count=100):
from sqlalchemy.exc import IntegrityError
from random import seed
import forgerypy
seed()
for i in range(count):
u = User(email=forgery_py.internet.emial_address(),
username=forgery_py.internet.user_name(True),
password=forgery_py.lorem_ipsum.word(),
confirmed=True,
name=forgery_py.name.full_name(),
location=forgery_py.address.city(),
about_me=forgery_py.lorem_ipsum.sentence(),
member_since=forgery_py.date.date(True))
db.session.add(u)
try:
db.session.commit()
except IntegrityError:
db.session.rollback()
class Post(db.Model):
#...
@staticmethod
def generate_fake(count=100):
from random import seed, randint
import forgery_py
seed()
user_count = User.query.count()
for i in range(count):
u = User.query.offset(randint(0, user_count - 1)).first()
p = Post(body=forgery_py.lorem_ipsum.sentences(randint(1, 3)),
timestamp=forgery_py.date.date(True),
author=u)
db.session.add(p)
db.session.commit()
forgerypy产生信息是完全随机的，所以在生成用户时可能会生成相同的用户不符合主键唯一原则造成插入失败，
所以使用try - except语句
调用函数生成数据
python manage.py shell
User.generate_fake(100)
Post.generate_fake(100)
Rendering Data on Pages
app/main/views.py
@main.route('/', methods=['GET', 'POST'])
def index():
#...
page = request.args.get('page', 1, type=int)
pagination = Post.query.order_by(Post.timestamp.desc()).paginate(
page, per_page=current_app.config['FLASKY_POSTS_PER_PAGE'],
error_out=False)
posts = pagination.items
return render_template('index.html', form=form,
posts=posts, pagination=pagination)
Adding a Pagination Widget
pagination()函数返回的是一个Pagination类的实例，该类有如下属性和方法
| Attribute | Description |
|---|---|
| items | The records in the current page |
| query | The source query that was paginated |
| page | The current page number |
| prev_num | The previous page number |
| next_num | The next page number |
| has_prev | True if there is a previous page |
| has_next | True if there is a next page |
| pages | the total number of pages for the query |
| per_page | the number of items per page |
| total | the total number of items returned by the query |
| Method | Description |
|---|---|
| iter_pages(left_edge=2, left_current=2, right_current=5, right_edge=2) | |
| prev() | a pagination object for the previous page |
| next() | a pagination object for the next page |
app/templates/_macros.html
{% macro pagination_widget(pagination, endpoint) %}
<ul class="pagination">
<li {% if not pagination.has_prev %} class="disabled"{% endif %}>
<a href="{% if pagination.has_prev %}{{ url_for(endpoint,
page=pagination.page-1, **kwargs) }}{% else %}#{% endif %}">
«
</a>
</li>
{% for p in pagination.iter_pages() %}
{% if p %}
{% if p == pagination.page %}
<li class="active">
<a href="{{ url_for(endpoint, page=p, **kwargs) }}">{{ p }}</a>
</li>
{% else %}
<li>
<a href="{{ url_for(endpoint, page=p, **kwargs) }}">{{ p }}</a>
</li>
{% endif %}
{% else %}
<li class="disabled"><a href="#">…</a></li>
{% endif %}
{% endfor %}
<li {% if not pagination.has_next %} class="disabled" {% endif %}>
<a href="{% if pagination.has_next %}{{ url_for(endpoint,
page=pagination.page+1, **kwargs) }}{% else %}#{% endif %}">
»
</a>
</li>
</ul>
{% endmacro %}
app/templates/index.html
{% extends "base.html" %}
{% import "bootstrap/wtf.html" as wtf %}
{% import "_macros.html" as macros %}
...
{% include '_posts.html' %}
<div class="pagination">
{{ macros.pagination_widget(pagination, '.index') }}
</div>
Rich-Text Posts with Markdown and Flask-PageDown
安装必要的package
pip install flask-pagedown markdown bleach
Using Flask-PageDown
Flask-PageDown拓展定义了PageDownField类，它和WTForms中的TextAreaField有着相同的接口
在使用前，需要将其初始化
app/__init__.py
from flask.ext.pagedown import PageDown
# ...
pagedown = PageDown()
# ...
def create_app(config_name):
# ...
pagedown.init_app(app)
# ...
修改app/main/forms.py中的PostForm()
from flask_pagedown.fields import PageDownField
class PostForm(Form):
body = PageDownField("What's on your mind?", validators=[Required()])
submit = SubmitField('Submit')
app/templates/index.html中添加脚本
{% block scripts %}
{{ super() }}
{{ pagedown.include_pagedown() }}
{% endblock %}
Handling Rich Text on the Server
保存博客表单时，只保存原始markdown数据，所以再次显示时需要重新转换成html
app/models.py
from markdown import markdown
import bleach
class Post(db.Model):
#...
body_html = db.Column(db.Text)
#...
@staticmethod
def on_changed_body(target, value, oldvalue, initiator):
allowed_tags = ['a', 'abbr', 'acronym', 'b', 'blockquote', 'code',
'em', 'i', 'li', 'ol', 'pre', 'strong', 'ul',
'h1', 'h2', 'h3', 'p']
target.body_html = bleach.linkify(bleach.clean(
markdown(value, output_format='html'),
tags=allowed_tags, strip=True))
db.event.listen(Post.body, 'set', Post.on_changed_body)
更新数据库
python manage.py db migrate -m "markdown"
python manage.py db upgrade
app/templates/_posts.html
...
<div class="post-body">
{% if post.body_html %}
{{ post.body_html | safe }}
{% else %}
{{ post.body }}
{% endif%}
</div>
...
Permanent Links to Blog Posts
为了分享单独一片文件，需要每片博客有独立的固定URL
app/main/views.py
@main.route('/post/<int:id>')
def post(id):
post = Post.query.get_or_404(id)
return render_template('post.html', posts=[post])
注意传给post.html页面中的是一个博客列表，虽然其中只有一个元素。采用这种方式是为了在这个页面中使用_posts.html
app/templates/post.html
{% extends "base.html" %}
{% block title %}Flasky - Post{% endblock %}
{% block page_content %}
{% include '_posts.html' %}
{% endblock %}
同时在_posts.html中添加到单片博客的连接
app/templates/_posts.html
<ul class="posts">
{% for post in posts %}
<li class="post">
...
<div class="post-content">
<a href="{{ url_for('.post', id=post.id) }}">
<span class="label label-default">Permalink</span>
</a>
</div>
</li>
{% endfor %}
</ul>
{% raw %}
Blog Post Editor
app/templates/edit_post.html
{% raw %}
{% extends "base.html" %}
{% import "bootstrap/wtf.html" as wtf %}
{% block title %}{% endblock %}
{% block page_content %}
<div class="page-header">
<h1>Edit Post</h1>
</div>
<div>
{{ wtf.quick_form(form) }}
</div>
{% endblock %}
{% block scripts %}
{{ super() }}
{{ pagedown.include_pagedown() }}
{% endblock %}
app/main/views.py
@main.route('/edit/<int:id>', methods=['GET', 'POST'])
@login_required
def edit(id):
post = Post.query.get_or_404(id)
if current_user != post.author and \
not current_user.can(Permission.ADMINISTER):
abort(403)
form = PostForm()
if form.validate_on_submit():
post.body = form.body.data
db.session.add(post)
flash('the post has been updated.')
return redirect(url_for('post', id=post.id))
form.body.data = post.body
return render_template('edit_post.html', form=form)
app/templates/_posts.html
<ul class="posts">
{% for post in posts %}
<li class="post">
...
<div class="post-content">
...
<div class="post-footer">
...
{% if current_user == post.author %}
<a href="{{ url_for('.edit', id=post.id) }}">
<span class="label label-primary">Edit</span>
</a>
{% elif current_user.is_administrator() %}
<a href="{{ url_for('.edit', id=post.id) }}">
<span class="label label-danger">Edit[Admin]</span>
</a>
{% endif %}
</div>
</div>
</li>
{% endfor %}
</ul>
