Question

我对如何使用Model创建ActiveAndroid并使其具有两个与Cascade条件onDelete相关的表感到困惑，并且找不到任何好/清晰的方法值得学习的例子。所以我有这张桌子：

    @Table(name = "CheckList")
    public class CheckList {

    @Column(name = "Title")
    String Title;
    @Column(name = "After")
    Integer After;
    @Column(name = "Before")
    Integer Before;

    @Column(name = "Enabled")
    Boolean Enabled;

    @Column(name = "Info")
    String Info;
}

并且我需要在此表中列出它：

@Table(name = "Equipment")
public class Equipment {

    @Column(name = "Title")
    String Title;

    @Column(name = "Checklists")
    List<CheckList> Checklists;

}

我可能还有另一个带有Equipment列表的表，我需要像上面那样将它们关联起来。

我想要的是，当我从Equipment删除记录时，我也需要删除List<CheckList> Checklists;中与此Equipment相关的所有记录。我知道我可以进行查询等等，但是我需要知道是否有更好的方法和正确的方法来做到这一点？

请详细说明（如何创建关系和稍后查询），并显示与我的表相关的示例。

Answer 1

您需要使用外键级联关系设置表。

@Table(name = "Equipment")
public class Equipment {

    @Column(name = "Title")
    String Title;

    // This method is optional & does not affect the foreign key creation.
    public List<CheckList> items() {
        return getMany(CheckList.class, "Equipment");
    }
}

@Table(name = "CheckList")
public class CheckList {

    @Column(name = "Title")
    String Title;

    @Column(name = "After")
    Integer After;

    @Column(name = "Before")
    Integer Before;

    @Column(name = "Enabled")
    Boolean Enabled;

    @Column(name = "Info")
    String Info;

    //This establishes a relationship between Checklist and Equipment, Any update or delete operations done on Equipment table gets cascaded to the corresponding rows in the Checklist table.
    @Column(name = "Equipment", onUpdate = ForeignKeyAction.CASCADE, onDelete = ForeignKeyAction.CASCADE)
    Equipment equipment;

}

与Cascade的ActiveAndroid一对多关系

1 个答案:

参考资料：