Gorm updates 子结构体空值更新

要通过struct更新，可以通过SELECT指定空值字段

但是如何指定子结构体的空字段呢

type A struct{
    Id int64 `gorm:"column:id"`
    Name string `gorm:"column:name"`
    Extra B `gorm:"foreignkey:Aid;references:Id;"`
}
type B struct{
   Aid int64 `gorm:"column:a_id"`
   Title string `gorm:"column:title"`
}

数据格式：
   data:={
       Id:2,
       Name:"张三",
       Extra:{
             Title:""
       }
   }
   db.Select([]string{"Name","Extra"}).updates(&data)

这是无法更新B的数据 请问这应该如何处理

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Expected answer

Comment From: jinzhu

We won't update associations to blank ,even it is selected. for normal fields it should works.

What's your situations for the issue?