7

我无法在 ndb 分页中进入“上一页”。

我在这里检查了文档和类似的问题，但没有成功。

 def show_feedback(kind, bookmark=None):
    """Renders returned feedback."""
    cursor = None    
    more_p= None
    if bookmark:
        cursor = Cursor(urlsafe=bookmark)

    q = Feedback.query()
    q_forward = q.filter(Feedback.kind==Feedback.KINDS[kind]).order(-Feedback.pub_date)
    q_reverse = q.filter(Feedback.kind==Feedback.KINDS[kind]).order(Feedback.pub_date)

    feedbacks, next_cursor, more = q_forward.fetch_page(app.config['FEEDBACK_PER_PAGE'], start_cursor=cursor)
    if cursor:
        rev_cursor = cursor.reversed()
        feedbacks2, prev_cursor, more_p = q_reverse.fetch_page(app.config['FEEDBACK_PER_PAGE'], start_cursor=rev_cursor)

    next_bookmark = None
    prev_bookmark = None
    if more and next_cursor:
        next_bookmark = next_cursor.urlsafe()
    if more_p and prev_cursor:
        prev_bookmark = prev_cursor.urlsafe()
    return render_template_f11('show_feedback.html', kind=kind, feedbacks=feedbacks, next_bookmark=next_bookmark, prev_bookmark=prev_bookmark)

html:

  {% if prev_bookmark %}
        <a href="{{ url_for(request.endpoint, bookmark=prev_bookmark) }}">Previous</a>
  {% endif %}
  {% if next_bookmark %}
    <a href="{{ url_for(request.endpoint, bookmark=next_bookmark) }}">Next</a>
  {% endif %}

我可以正确翻页直到结束。但是我不能向后翻页直到最后一页，即使那样我也不能向后翻页直到第一页。

请问我错过了什么？

更新：

根据 Faisal 的建议更改了代码。我必须承认它的效果更好。但是分页仍然无法正常工作：

我有 7 个条目。配置中的 PAGE_SIZE 为 3。因此我们得到三个页面：

单击下一步时，我得到 7,6,5 -> 4,3,2 -> 1 Perfect。现在点击上一个时：1 -> 3,4,5 (?) -> 5,6,7 (?)

谢谢你的帮助

def show_feedback(kind, bookmark=None):
    """Renders returned feedback."""
    is_prev = request.args.get('prev', False)
    cursor = None        
    if bookmark:
        cursor = Cursor(urlsafe=bookmark)

    q = Feedback.query()
    q_forward = q.filter(Feedback.kind==Feedback.KINDS[kind]).order(-Feedback.pub_date)
    q_reverse = q.filter(Feedback.kind==Feedback.KINDS[kind]).order(Feedback.pub_date)

    qry = q_reverse if is_prev else q_forward

    feedbacks, cursor, more = qry.fetch_page(app.config['FEEDBACK_PER_PAGE'], start_cursor=cursor)

    if is_prev:
        prev_bookmark = cursor.reversed().urlsafe() if more else None
        next_bookmark = bookmark
    else:
        prev_bookmark = bookmark
        next_bookmark = cursor.urlsafe() if more else None
    return render_template_f11('show_feedback.html', kind=kind, feedbacks=feedbacks, next_bookmark=next_bookmark, prev_bookmark=prev_bookmark)

更新 2：

现在看来它几乎可以使用 reverse()。

7,6,5 -> 下一个 -> 4,3,2 -> 下一个 -> 1

1 -> prev -> 2,3,4 -> 5,6,7 （订单不再是最晚日期优先）

4

2 回答 2

9

所以我在这里做的是使用当前书签来导航下一个或上一个并删除另一个查询，因此它不会为每个请求查询两次。（当我测试它时，编辑旧的描述/答案是错误的。这个适用于我的本地主机）。

尝试：

is_prev = self.request.get('prev', False)
if is_prev:
    qry = q_reverse
    cursor = cursor.reversed()
else:
    qry = q_forward

feedbacks, cursor, more = qry.fetch_page(app.config['FEEDBACK_PER_PAGE'], start_cursor=cursor)

if is_prev:
    prev_bookmark = cursor.reversed().urlsafe() if more else None
    next_bookmark = bookmark
else:
    prev_bookmark = bookmark
    next_bookmark = cursor.urlsafe() if more else None

html

{% if prev_bookmark %}
    <a href="{{ url_for(request.endpoint, bookmark=prev_bookmark, prev=True) }}">Previous</a>
{% endif %}
{% if next_bookmark %}
  <a href="{{ url_for(request.endpoint, bookmark=next_bookmark) }}">Next</a>
{% endif %}
于 2013-07-31T16:30:49.893 回答
0

在这里，您有一个完整的工作解决方案。你的代码有问题。

他们的关键是在倒退时扭转结果。这很棘手。

在这里你有：

def return_query_page(query_class, size=10, bookmark=None, is_prev=None, equality_filters=None, orders=None):
    """
    Generate a paginated result on any class
    Param query_class: The ndb model class to query
    Param size: The size of the results
    Param bokkmark: The urlsafe cursor of the previous queries. First time will be None
    Param is_prev: If your requesting for a next result or the previous ones
    Param equal_filters: a dictionary of {'property': value} to apply equality filters only
    Param orders: a dictionary of {'property': '-' or ''} to order the results like .order(cls.property)
    Return: a tuple (list of results, Previous cursor bookmark, Next cursor bookmark)
    """
    if bookmark:
        cursor = ndb.Cursor(urlsafe=bookmark)
    else:
        is_prev = None
        cursor = None

    q = query_class.query()
    try:
        for prop, value in equality_filters.iteritems():
            q = q.filter(getattr(query_class, prop) == value)

        q_forward = q.filter()
        q_reverse = q.filter()

        for prop, value in orders.iteritems():
            if value == '-':
                q_forward = q_forward.order(-getattr(query_class, prop))
                q_reverse = q_reverse.order(getattr(query_class, prop))
            else:
                q_forward = q_forward.order(getattr(query_class, prop))
                q_reverse = q_reverse.order(-getattr(query_class, prop))
    except:
        return None, None, None
    if is_prev:
        qry = q_reverse
        new_cursor = cursor.reversed() if cursor else None
    else:
        qry = q_forward
        new_cursor = cursor if cursor else None

    results, new_cursor, more = qry.fetch_page(size, start_cursor=new_cursor)
    if more and new_cursor:
        more = True
    else:
        more = False

    if is_prev:
        prev_bookmark = new_cursor.reversed().urlsafe() if more else None
        next_bookmark = bookmark
        results.reverse()
    else:
        prev_bookmark = bookmark
        next_bookmark = new_cursor.urlsafe() if more else None

    return results, prev_bookmark, next_bookmark

这是 github 项目的链接：https ://github.com/janscas/ndb-gae-pagination

于 2014-04-30T09:12:26.907 回答