Question

我正在通过Miguel Grinberg的Flask Mega Tutorial工作，我无法弄清楚为什么索引页面现在无法加载。这是追溯：

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask_login.py", line 658, in decorated_view
return func(*args, **kwargs)

File "/home/asdoylejr/microblog/app/views.py", line 44, in index
posts = posts)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/templating.py", line 128, in render_template
context, ctx.app)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/templating.py", line 110, in _render
rv = template.render(context)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 969, in render
return self.environment.handle_exception(exc_info, True)

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 742, in handle_exception
reraise(exc_type, exc_value, tb)

File "/home/asdoylejr/microblog/app/templates/index.html", line 2, in top-level template code
{% extends "base.html" %}

File "/home/asdoylejr/microblog/app/templates/base.html", line 30, in top-level template code
{% block content %}{% endblock %}

File "/home/asdoylejr/microblog/app/templates/index.html", line 7, in block "content"
{{form.hidden_tag()}}

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 397, in getattr
return getattr(obj, attribute)

UndefinedError: 'form' is undefined

以下是相关索引页面的代码：

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

{% block content %}
<h1>Hi, {{g.user.nickname}}!</h1>
<form action="" method="post" name="post">
    {{form.hidden_tag()}}
<table>
    <tr>
        <td>Say something:</td>
        <td>{{form.post(size = 30, maxlength = 140)}}</td>
        <td>
        {% for error in form.errors.post %}
        <span style="color: red;">[{{error}}]</span><br>
        {% endfor %}
        </td>
    </tr>
    <tr>
        <td></td>
        <td><input type="submit" value="Post!"></td>
        <td></td>
    </tr>
</table>
</form>
{% for post in posts %}
<p>
    {{post.author.nickname}} says: <b>{{post.body}}</b>
</p>
{% endfor %}
{% endblock %}

以下是视图中的代码：

@app.route('/', methods = ['GET', 'POST'])
@app.route('/index', methods = ['GET', 'POST'])
@login_required
def index():
    form = PostForm()
    if form.validate_on_submit():
        post = Post(body = form.post.data, timestamp = datetime.utcnow(), author = g.user)
        db.session.add(post)
        db.session.commit()
        flash('Your post is now live!')
        return redirect(url_for('index'))
    posts = g.user.followed_posts().all()
    return render_template("index.html",
        title = 'Home',
        user = user,
        posts = posts)

我已多次阅读本教程，并将我的代码与他在每节课结束时发布的源代码进行比较，我不知道为什么它不起作用。我不确定为什么它在这个视图中传递表单时没有返回错误在另一个视图中传递表单时出错。

有人能指出我正确的方向吗？

Answer 1

您收到的错误消息在堆栈跟踪中进行了说明。具体来说，这里：

File "/home/asdoylejr/microblog/app/templates/index.html", line 7, in block "content"
{{form.hidden_tag()}}

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 397, in getattr
return getattr(obj, attribute)

UndefinedError: 'form' is undefined

错误消息来自Jinja，它说form未定义。您的模板尝试使用form ...

...
{% block content %}
<h1>Hi, {{g.user.nickname}}!</h1>
<form action="" method="post" name="post">
    {{form.hidden_tag()}}
<table>
    ...

...但您从未将其作为render_template方法的一部分传递（您只定义了title，user和posts）...

return render_template("index.html",
        title = 'Home',
        user = user,
        posts = posts)

Answer 2

您应该将form作为上下文变量传递。试试这个：

@app.route('/', methods = ['GET', 'POST'])
@app.route('/index', methods = ['GET', 'POST'])
@login_required
def index():
    form = PostForm()
    if form.validate_on_submit():
        post = Post(body = form.post.data, timestamp = datetime.utcnow(), author = g.user)
        db.session.add(post)
        db.session.commit()
        flash('Your post is now live!')
        return redirect(url_for('index'))
    posts = g.user.followed_posts().all()
    return render_template("index.html",
        title = 'Home',
        user = user,
        posts = posts,
        form = form)

Answer 3

您没有在模板中传递“表单”。

因为它是html模板的一部分。

return render_template("index.html",
        title = 'Home',
        user = user,
        posts = posts,
        form = form) # <<<-------------------- Here.

Flask Mega教程 - jinja2.exceptions.UndefinedError：'form'未定义

3 个答案: