当我们用另一个结构包装时，Gorm golang sql.NullInt64无法正常工作

Question

User can be deleted by another user. In that case,

type User struct {
    gorm.Model
    Email string `gorm:"type:varchar(100)"`
    DeletedBy     sql.NullInt64
}

DeletedBy will be null when we create a new user. So I used sql.NullInt64 instead of int64. But I cannot convert to JSON.

{ "Email": "xxxxx", "DeletedBy": {"Int64":2,"Valid":true} }

For that, I tried https://gist.github.com/smagch/bc34f861df65c8ea2e90 But Gorm send query condition value as "[{2, true}]"

Answer 1

In Go when you declare a type as an alias of another type, the new type does not get to keep the other type's methods. So here:

type NullInt64 sql.NullInt64

your new NullInt64 type has the same structure and memory layout as sql.NullInt64 but it does not have its methods, namely the Scan and Value methods required for it to work the way you want.

Instead what you can do is to embed the sql.NullInt64 and you should be good to go.

type NullInt64 struct {
    sql.NullInt64
}