如何在Freemarker中按日期对对象列表进行分组？

Question

<#setting date_format="dd/MM/yyyy">
<#assign data1 = "14/05/2016" />
<#assign data2 = "20/05/2016" />
<#assign data3 = "19/06/2016" />
<#assign events_list = [
  {"name":"Event Lorem", "date":data1?date},
  {"name":"Event Lipsum", "date":data2?date},
  {"name":"Event Free", "date":data2?date},
  {"name":"Event Dolor", "date":data3?date},
  {"name":"Event Sit", "date":data1?date}
] />

我有这个事件列表，我按日期排序：

<h5>Order by date:</h5>
<#list events_list?sort_by("date") as event>
    <p>${event.name}: ${event.date}</p>
</#list>

现在我想按日期分组，因为每个人都可以有几个小时 就像在这个例子中一样：

如何在Freemarker中完成此操作？

Answer 1

<#setting date_format="dd/MM/yyyy">
<#assign dataNull = "01/01/1900" />
<#assign data1 = "14/05/2016" />
<#assign data2 = "20/05/2016" />
<#assign data3 = "19/06/2016" />
<#assign events_list = [
  {"name":"Event Lorem", "date":data1?date},
  {"name":"Event Lipsum", "date":data2?date},
  {"name":"Event Free", "date":data2?date},
  {"name":"Event Dolor", "date":data3?date},
  {"name":"Event Sit", "date":data1?date}
] />




<h5>Order by date:</h5>
<#assign lastDate = dataNull?date>
<#list events_list?sort_by("date") as event>

    <#if lastDate != event.date >
      <p><b> ${event.date}</b></p>
    </#if>

    <#assign lastDate = event.date >
    <p>${event.name}: ${event.date}</p>

</#list>

按日期排序：

14/05/2016

活动Lorem：14/05/2016 2016/05/14

活动时间：14/05/2016 2016/05/14

20/05/2016

活动Lipsum：20/05/2016 20/05/2016

免费活动：20/05/2016 20/05/2016

19/06/2016

活动Dolor：19/06/2016 19/06/2016

Answer 2

另请参阅此答案，以了解如何使用宏实施分组列表。我认为这比其他答案更可重复使用：https://stackoverflow.com/a/61588885/606679