在Bluelog项目完成后，删除分类会提示分类已删除，之后访问主页等页面后会报错。
jinja2.exceptions.UndefinedError: 'None' has no attribute 'id'
在加上debug信息删除分类提示：
SAWarning: DELETE statement on table 'category' expected to delete 1 row(s); 0 were matched. Please set confirm_deleted_rows=False within the mapper configuration to prevent this warning.
% (table.description, expected, rows_matched)
从上面分析得出，可能是分类删掉了，其下文章没有划分到默认分类上？？
代码上基本与源码仓库对照过了，没有问题。
以下是部分主要代码
@admin_bp.route('/category/<int:category_id>/delete', methods=['POST'])
@login_required
def delete_category(category_id):
category = Category.query.get_or_404(category_id)
if category.id == 1:
flash('You can not delete the default category.', 'warning')
return redirect(url_for('blog.index'))
category.delete() # 调用category对象的delete()方法删除分类
flash('Category deleted.', 'success')
return redirect(url_for('admin.manage_category'))
@blog_bp.route('/category/<int:category_id>')
def show_category(category_id):
category = Category.query.get_or_404(category_id)
page = request.args.get('page', 1, type=int)
per_page = current_app.config['BLUELOG_POST_PER_PAGE']
pagination = Post.query.with_parent(category).order_by(Post.timestamp.desc()).paginate(page, per_page)
posts = pagination.items
return render_template('blog/category.html', category=category, pagination=pagination, posts=posts)
class Category(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), unique=True)
posts = db.relationship('Post', back_populates='category')
# 定义delete属性，删除分类后，该分类下的文章不会被删除，会放到默认分类中。
def delete(self):
default_category = Category.query.get(1)
posts = self.posts[:]
for post in posts:
post.category = default_category
db.session.delete(self)
db.session.commit()
谢谢。
