SilverStripe：使用 has_many 关系对 DataObject 进行排序

Question

在 SilverStripe 中，我有一个事件数据对象

class Event extends DataObject {
    private static $db = array(
        'Name'          => 'Text'
    );

    private static $has_many = array(
        'EventDates'    => 'EventDate'

有很多活动日期：

class EventDate extends DataObject {
    private static $db = array(
        'Day'          => 'Date',
        'StartTime'     => 'Varchar',
        'EndTime'       => 'Varchar'    
    );

现在，如果我查询页面上的所有事件，例如

Event::get()

我希望它们按最早日期排序。

哪种方式最适合实现这一目标？

Answer 1

您可以使用默认排序规则在 DataObject 类上定义静态属性：

<?php

  class EventDate extends DataObject {

    …
    // This also effects the default sorting of `has_many` related Events.
    private static $default_sort = "\"Day\" ASC";

  }

?>

现在

<?php

  // first we pick a Event object, for instance by a (given) $id
  $event = Event::get()->byId($id);
  // because the default sort ist Day the attached `EventDate` will now be sorted by `Day` if you don't specify otherwise
  $events = $event->EventDates();
  // will return the earliest Event (of course you don't filter events here which are in the past).
  $firstEvent = $events->First();

  // if you then want to sort differently at some place, you can call ->sort() on the list:
  $event = Event::get()->byId($id);
  $events = $event->EventDates()->sort('LastEdited', 'DESC');
  $lastEditedEvent = $events->First();

?>