I'm using PostgreSQL and GORM in my Go app.
I thought that using the sql tab of sql:"not null" would do the trick of preventing a null entry, but when go initializes structs with a string type then it defaults to an empty string which is not the same as null in the db.
I am wondering if there is a way to prevent this from happening in a struct definition so I wouldn't have to strictly enforce it at all levels in the application code.
You can solve this problem of preventing '' (empty) string insertion into the database by using default: null and not null constraint together. SO if Struct field values are empty it will be consider as default value null and gorm will throw an error.
gorm:"unique;not null;type:varchar(100);default:null"
Example is:
type User struct {
gorm.Model
Email string `gorm:"unique;not null;type:varchar(100);default:null"`
}
SO gorm for empty User.Email will throw an error.
ERROR: null value in column "email" of relation "users" violates not-null constraint (SQLSTATE 23502)
A reasonable approach is using a BeforeCreate hook to validate the Email field and return an error if it is empty string. This way, you can ensure that object is only created when the required fields are properly populated.
// BeforeCreate hook to validate email field
func (u *User) BeforeCreate(tx *gorm.DB) (err error) {
if u.Email == "" {
return errors.New("email cannot be empty")
}
return nil
}
type User struct {
gorm.Model
Email string `gorm:"unique;not null;type:varchar(100);default:null"`
}
When I use like this it works but when I automigrate I did had error from migration gorm
Add a isValid() function to your model that returns false if a not null field is in its defalt (0 for int, "" for string, etc), and before insert, check if valid, return an error if not valid, else, nil.
