如何查询特定对象类型的继承对象的集合? [英] How to query a collection of inherited object for a particular object type in grails?

问题描述

我有一个这样的模型:

class Question{
  Set components
  static hasMany = [components: QuestionComponent]
}

class QuestionComponent{
  static belongsTo = Question
}

class QuestionComponentStatus extends QuestionComponent{

}
class QuestionComponentOther extends QuestionComponent{

}

我只想从Set组件中获取QuestionComponentStatus:

I want to get only QuestionComponentStatus from Set components :

questionInstance.components. ?

questionInstance.components. ?

非常感谢

推荐答案

您可以直接在子类上进行查询以避免多态结果.假设您的一对多关系是双向的(即static belongsTo = [question: Question])，则可以执行以下操作:

You can just do a query directly on the subclass to avoid polymorphic results. Provided that your one-to-many relationship is bi-directional (i.e. static belongsTo = [question: Question]), you could do something like:

QuestionComponentStatus.findAllByQuestion(q)

或在HQL中:

QuestionComponentStatus.findAll("FROM QuestionComponentStatus WHERE question = :question", [question: q])

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