In the update trigger, you need to delete the corresponding feature if one of the coordinates becomes null.
在更新触发器中，如果坐标值之一变成null，那么需要删除对应的特性。
The update trigger is more complicated: if the update causes an exception, you have to delete the existing feature row, just as for null coordinates.
更新触发器比较复杂：如果更新导致异常，那么必须删除现有的特性行，就像处理null坐标一样。
An alternative way of creating a heap dump is to use another useful Rubinius feature: the Query Agent, which allows monitoring tools to access Rubinius information as well as trigger certain actions.
创建堆转储的另外一种方式是使用Rubinius的另一个特性：QueryAgent，监测工具可以凭借它访问Rubinius信息并触发某些动作。
With knowledge of the user's preference, you can trigger the alert as closely as possible to the feature that requires location information, or perhaps avoid it altogether.
获取了用户对位置服务的预设以后，你就可以只为那些非常紧密地非常可能需要用户位置信息的功能，触发提醒，或者说，完全地避免这些提醒。
If you're in an open place, look around after selecting the Sentry Gun and you will see a grid appear which indicates the line where enemies cross to trigger the auto-aim feature of the Sentry Gun.
当你在空旷区域放置步哨时，仔细观察四周你将会看到一层网格，表示步哨将会自动攻击此范围中的敌人。
If you're in an open place, look around after selecting the Sentry Gun and you will see a grid appear which indicates the line where enemies cross to trigger the auto-aim feature of the Sentry Gun.
当你在空旷区域放置步哨时，仔细观察四周你将会看到一层网格，表示步哨将会自动攻击此范围中的敌人。
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