属于多个域 [英] belongsTo multiple Domain

问题描述

我有4个类，事件，问题，请求，另外一个是附件.

I have 4 classes, incidents,problems, requests and another is Attachment.

每个域都看起来像.........

Every domain look like.........

    Class Incidents
    {
    // other fields
       static hasOne = [attachment: Attachment]

       static constraints = [attachment nullable:true]
    }

    Class Problems
    {
    // other fields
       static hasOne = [attachment: Attachment]

       static constraints = [attachment nullable:true]
    }

    Class Requests
    {
    // other fields
       static hasOne = [attachment: Attachment]

       static constraints = [attachment nullable:true]
    }

    Class Attachment
    {
    // other fields
       static belongsTo= [
                   incident: Incidents, 
                   problem: Problems,
                   requests: Requests
]

   static constraints = {
        incident nullable: true
        problem nullable: true
        requests nullable: true
}

当我保存事件对象时，它会引发异常，例如列'problem_id'不能为null. 该怎么办?

when I am saving object of incident, it throws exception like Column 'problem_id' cannot be null. what to do?

推荐答案

尝试删除有关事件，问题，请求的hasOne并将其替换为

Try to remove the hasOne on Class Incidents, Problems, Requests and replace it with

   Attachment attachment
   static constraints = {attachment: unique: true, nullable:true}       
   static mapping = {
    attachment  cascade: "delete"
    }

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