在使用for循环时，如何只打印一次“收到日期”？ [英] How can I print the 'date received' only one time while using a for loop?

问题描述

我正在尝试按今天收到的消息，昨天收到的消息等对消息进行分组。为澄清起见，我尝试使用一个标有 Today的标头，然后在下面列出这些消息。我不是要打印今天以及当天收到的每条消息（目前正在发生这种情况）。

I am trying to group messages by received today, received yesterday, ect. To clarify, I am trying to have a single header that says "Today" and then list those messages underneath. I am NOT trying to print "Today" along with each message that was received on that day (which is currently what's happening).

我目前有TODAY和YESTERDAY标头在我的for循环内部，所以我知道这就是为什么要为每封邮件打印这些标头，但是如前所述，我只想打印一次。我的问题是，如何使用下面的代码实现这一目标？我是否需要针对每个时间段（今天，昨天，上周等）进行单独的for循环，还是有一种更有效的方法？

I currently have the TODAY and YESTERDAY headers inside of my for loop so I understand that is why it is printing these headers for each mail message, but as previously stated I just want to print them one time. My question is, how can I achieve this using the code below? Do I need to make separate for loops for each time period (today, yesterday, last week, ect.), or is there a more efficient way to do this?

{% for message in messages %}
    {% if message.date - current.date < 24 hours %}
        TODAY
        Sent by: {{ message.sender }}
        {{ message.body }}
    {% elif message.date - current.date > 24 hours and message.date - current.date < 48 hours %}
        YESTERDAY
        Sent by: {{ message.sender }}
        {{ message.body }
    {% endif %}
{% endfor %}

推荐答案

您可以使用 {{forloop.first}} 为此。因此，您的代码可以更新为

You can use {{forloop.first}} for this. So your code can be updated to

{% for message in messages %}
    {% if message.date - current.date < 24 hours %}
        {% if forloop.first %}
            TODAY
        {% endif %}
    {% elif message.date - current.date > 24 hours and message.date - current.date < 48 hours %}
       {% if forloop.first %}
        YESTERDAY
       {% endif %}
    {% endif %}

    Sent by: {{ message.sender }}
    {{ message.body }}

{% endfor %}

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