我如何获得一个类的实例而不是它的子类？ [英] How do I get an Instance of a class instead of its subclass?

问题描述

我有2个域名：

事件：

  class事件{
字符串标题
字符串描述
} 
 
静态映射= {
 tablePerHierarchy（false）
} 
  

以及事件延伸的IncidentWithTimers：



  class IncidentWithTimers extends Incident {
 int currentResponseTime 
 Date responseTimeEndDate 
} 
  

IncidentWithTimers不是数据库中的实际表，它是数据库视图。

现在，当我尝试从控制器获取事件实例时，它以某种方式返回IncidentWithTimers实例：

  def index（）{
事件curIncident = Incident.get（params.incident）
 println（curIncident.getClass（））//class IncidentWithTimers
} 
  

由于该域是一个视图，因此我通过在<$ c中引发异常来禁用所有修改在IncidentWithTimers类中，$ c> beforeInsert / 更新 / 删除。

当我尝试修改并保存curIncident时，它会尝试访问 beforeUpdate（），并引发错误，同时我从来不希望首先更改 IncidentWithTimers 。

我能做些什么？

解决方案

问题是该视图包含每个事件，而不是它们的子集就像子类一样。正如你所说，每一个 IncidentWithTimers 都是事件。

解决方案是使用查询而不是子类，或者使 IncidentWithTimers 为独立的重复类而不是一个子类。

我认为前者是最好的选择，因为其意图很明确。

I have 2 domains:

Incident:

class Incident {
    String title
    String description
}

static mapping = {
    tablePerHierarchy(false)
}

And IncidentWithTimers which extends Incident:

class IncidentWithTimers extends Incident {
    int currentResponseTime
    Date responseTimeEndDate
}

IncidentWithTimers is not an actual table in the database, it's a database view.

Now when I try to get an Incident instance from a controller, it somehow returns an IncidentWithTimers instance:

def index() {
    Incident curIncident = Incident.get(params.incident)
    println(curIncident.getClass())// "class IncidentWithTimers"
}

Since this domain is a view, I disabled all modifications by throwing exceptions in the beforeInsert/Update/Delete, in the IncidentWithTimers class.

When I try to modify and save the curIncident, it tries to access the beforeUpdate(), and throws the error, while I never wanted to change the IncidentWithTimers in the first place.

What can I do about this?

解决方案

The problem is that the view includes every Incident, not a subset of them as would happen with a subclass. As you said, every IncidentWithTimers is an Incident.

The solution is to either use a query instead of a subclass, or make IncidentWithTimers an independent duplicate class rather than a subclass.

I think the former is the best option because the intent is clear.

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