如果answer不存在的话会导致无法访问对应的问题页面

同学，你好！可以在detail()视图函数中添加条件判断，若answer不存在，则跳转到新的页面去添加回答

answer.html：

{% extends 'base_layout.html' %}
{% from 'macro/form_errors.html' import form_field_errors %}
{% block title %}{{ super() }} - 写回答{% endblock %}
{% block header %}
  <link rel="stylesheet" href="/assets/style/write.css">
  {% endblock %}
{% block content %}
  <div class="container">
    <div class="row">
      <div class="col-md-8 col-md-offset-2">
        <form class="form-horizontal write-form" method="post"
          enctype="multipart/form-data" action="{{ url_for('qa.detail', q_id=question.id) }}">
          {{ form.csrf_token }}
          <div class="form-group">
            <button type="submit" class="btn btn-info pull-right">发布</button>
          </div>
          <div class="form-group">
            {{ form.content }}
            {{ ckeditor.load() }}
            {{ ckeditor.config(name='content') }}
          </div>
          {{ form_field_errors(form.content.errors) }}
        </form>
      </div>
    </div>
  </div>
{% endblock %}

视图函数：

@qa.route('/detail/<int:q_id>', methods=['GET', 'POST'])
def detail(q_id):
    """ 问题详情 """
    # 1. 查询问题信息
    question = Question.query.get(q_id)
    if not question.is_valid:
        abort(404)
    # 2. 展示第一条回答信息
    answer = question.answer_list.filter_by(is_valid=True).first()
    if not answer:
        form = WriteAnswerForm()
        if form.validate_on_submit():
            if not current_user.is_authenticated:
                flash('请先登录', 'danger')
                return redirect(url_for('accounts.login'))
            form.save(question=question)
            flash('回答问题成功', 'success')
            answer = question.answer_list.filter_by(is_valid=True).first()
            return render_template('detail.html',question=question,answer=answer,form=form)
        return render_template('answer.html', form=form, question=question)
    else:
        form = WriteAnswerForm()
        if form.validate_on_submit():
            try:
                if not current_user.is_authenticated:
                    flash('请先登录', 'danger')
                    return redirect(url_for('accounts.login'))
                form.save(question=question)
                flash('回答问题成功', 'success')
                return redirect(url_for('qa.detail', q_id=q_id))
            except Exception as e:
                print(e)
        return render_template('detail.html',question=question,answer=answer,form=form)

祝学习愉快！