Flask 分页参数在重定向时重置答案

【问题标题】：Flask pagination arg resets on redirectFlask 分页参数在重定向时重置
【发布时间】：2022-01-24 13:44:24
【问题描述】：

所以我正在尝试使用我的数据库中的前 20 个“事件”设置一个索引页面，并可以选择进一步或后退。这是我的代码：

@app.route('/', methods=['GET', 'POST'])
def index():

    page = int(request.args.get('page', default=1, type=int))
    print("page is " + str(page))
    page_backwards = str((page - 1))
    print("page_backwards is " + page_backwards)
    page_forwards = str((page + 1))
    print("page_fowards is " + page_forwards)


    if request.method == 'GET':

        offset = int(20 * (page - 1))
        cursor = connection.cursor()

        if page <= 0:
            return redirect('/?page=1')

        if page == 1:
            events = cursor.execute(
                "SELECT name, date, time, venue, id FROM events ORDER BY date ASC LIMIT 20").fetchall()
            
        elif page > 1:
            events = cursor.execute(
                "SELECT name, date, time, venue, id FROM events ORDER BY date ASC LIMIT 20 OFFSET ?", (offset,)).fetchall()
        return render_template("index.html", events=events)

    if request.method == 'POST':

        if 'previous' in request.form:
            print("POST" + page_backwards)
            return redirect('/?page=' + page_backwards)
        elif 'next' in request.form:
            print("POST "+ page_forwards)
            return redirect('/?page=' + page_forwards)

它会更简洁，但我正在尝试调试它，这就是 page_backwards 等位于顶部的原因。

莫名其妙的部分是什么？

    if request.method == 'POST':

        if 'previous' in request.form:
            print("POST" + page_backwards)
            return redirect('/?page=' + page_backwards)
        elif 'next' in request.form:
            print("POST "+ page_forwards)
            return redirect('/?page=' + page_forwards)

这里的打印部分运行良好，它打印出正确的页面，但由于某种原因，返回重定向行为异常并被锁定到 1 和 2。

发生了什么：单击 PREVIOUS/NEXT 按钮后，它会将页面变量减去/添加 1，然后将该变量添加为参数。变量已正确更新，但无论发生什么，返回总是重定向到第 0 页（然后转到第 1 页）或第 2 页！！

这真是莫名其妙：

page is 5
page_backwards is 4
page_fowards is 6
127.0.0.1 - - [23/Dec/2021 16:29:49] "GET /?page=5 HTTP/1.1" 200 -
[...]
page is 1
page_backwards is 0
page_fowards is 2
POST 2
127.0.0.1 - - [23/Dec/2021 16:29:52] "POST / HTTP/1.1" 302 -
page is 2
page_backwards is 1
page_fowards is 3
127.0.0.1 - - [23/Dec/2021 16:29:52] "GET /?page=2 HTTP/1.1" 200 -

【问题讨论】：

据我了解，POST 请求似乎正在重置页面变量，因此默认为 1。我怎样才能阻止这种情况发生？

标签： python flask

【解决方案1】：

我想通了，POST 请求是完全独立的，它不会记住 URL 参数，因此将它们重置为默认值。最后我做了一个更干净的解决方法：

@app.route('/')
def index():

    page = int(request.args.get('page', default=1, type=int))

    offset = int(20 * (page - 1))
    cursor = connection.cursor()

    if page <= 0:
        return redirect('/?page=1')

    if page == 1:
        events = cursor.execute(
            "SELECT name, date, time, venue, id FROM events ORDER BY date ASC LIMIT 20").fetchall()
            
    elif page > 1:
        events = cursor.execute(
            "SELECT name, date, time, venue, id FROM events ORDER BY date ASC LIMIT 20 OFFSET ?", (offset,)).fetchall()
    return render_template("index.html", events=events, previous=str(page-1), next=str(page+1))

使用以下 HTML 代码：

  <form action="/" method="GET">
    <button name="page" value = "{{ previous }}"
      class="inline-flex items-center py-2 px-4 mr-3 text-sm font-medium text-gray-500 bg-white rounded-lg border border-gray-300 hover:bg-gray-100 hover:text-gray-700">
      ← Previous
    </button>
    <button name="page" value="{{ next }}"
      class="inline-flex items-center py-2 px-4 text-sm font-medium text-gray-500 bg-white rounded-lg border border-gray-300 hover:bg-gray-100 hover:text-gray-700">
      Next →

    </button>

【讨论】：