条目不会显示在烧瓶应用的模板页面上

Question

我无法从表单中获取数据库条目以显示在输出页面上。我认为这是我的flask-sqlalchemy查询，但我从文档中得不到任何内容。没有错误消息或回溯。代码如下：

表格页面的路线：

@app.route('/thing', methods=['GET', 'POST'])
def thing():
    form = TForm()
    return render_template(
        'thing.html',
        form=form,
        page_title = 'Add It', 
        form_submit_label = 'Add Entry')

表单操作的路线：

@app.route('/addthing', methods=['POST'])
def add_thing():
    form = TForm(request.form)
    filename = ''
    if request.method == 'POST' and form.validate_on_submit():
        cover = request.files['cover']
        if cover and allowed_file(cover.filename):
            filename = secure_filename(cover.filename)
            cover = cover.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
            return cover
        t = Thing(
            title = request.form['title'],
            genre = request.form['genre'],
            summary = request.form['summary'],
            cover = cover
        )
        db.session.add(t)
        db.session.commit()
     flash('New entry was successfully posted')
     return redirect(url_for('thinglist'))

模板路线：

@app.route('/thinglist', methods=['GET'])
def thinglist():
    thing_entries = Thing.query.all()
    # below thing_entries works, but it was just a way to test
    # thing_entries = [{'title': 'No where fast', 'genre': ['red', 'blue'], 'summary': 'I love trains'},
    # {'title': 'No why', 'genre': ['yellow', 'blue'], 'summary': 'I love lamp'},
    # {'title': 'where fast', 'genre': ['red', 'green'], 'summary': 'I love cats'}]
    return render_template(
        'thinglist.html',
        thing_entries=thing_entries,
        page_title = 'Thing List')

事物清单模板

{% extends "layout.html" %}
{% block content %}
{% for entry in thing_entries %}

<article>
    <div>
        <div>
            <img src="{{ entry.cover }}" alt="Cover for {{ entry.title }}" /> 
        </div>
        <div>
            <ul>
                <li class="">{{ entry.title }}</li>
                <li class=""><strong>Genre: </strong>{{ entry.genre }}</li>
                <li class=""><strong>Summary: </strong>{{ entry.summary|truncate( 30, true ) }}</li>
            </ul>
        </div>
    </div>
</article>

{% else %}

<div class="no-entries">Nothing</div>

{% endfor %}
{% endblock %}

我尝试了Thing.query.all（）行的许多变体，例如

Thing.query.filter_by(id=thing_id).all() ==> doesn't work
Thing.query.filter(thing_id) ==> doesn't work
Thing.query.get(thing_id) ==> doesn't work

我只是不明白。谢谢你的帮助。