Preload can't find field fieldName in *models.Catalog - go

Question

I can't find an answer to my question. I am using jinzhu/gorm in a golang project:)
I have the following structs:
type Catalog struct {
ID int64 `gorm:"primary_key" form:"id"`
SubDomainID int64 `form:"sub_domain_id"`
ServiceTypeID int64 `form:"service_type_id"`
Checked bool `form:"checked"`
CreatedAt time.Time `form:"created_at"`
UpdatedAt time.Time `form:"updated_at"`
SubDomain SubDomain
}
type SubDomain struct {
Id int64 `gorm:"primary_key" form:"id"`
NameRu string `form:name_ru`
url string `form:url`
}
When I try to get catalog with preloading of subdomain:
var catalog Catalog
fmt.Println(catalog.SubDomain)
err := db.Preload("SubDomain").Where("checked = 0").First(&catalog).Error
if err != nil {
return &catalog, err
}
I get the following error: can't find field SubDomain in *models.Catalog
Why is this happening?
I expect there will be 2 queries:
select * from catalogs where checked = 0;
select * from sub_domains where id = (catalog.sub_domain_id)

Answer 1

I'm still new to gorm, but I think I know your problem and also have a (partial) solution.
As stated before (and you said so yourself), when applying "select * from..." it also looks for the field SubDomain (because it is in your struct).
So I believe this should work:
var catalog Catalog
fmt.Println(catalog.SubDomain)
err := db.Preload("SubDomain").Select("ID","SubDomainID", "ServiceTypeID").Where("checked = 0").First(&catalog).Error
if err != nil {
return &catalog, err
}
note how i specified the exact fields. A better solution will be to write a function to exclude member which are fields, using reflection. I am using a similar solution myself. it kinda looks like this:
for each member of Domain:
if member is string or boolean
fields.append(member).
return db.Select(fields) // actual gormdb's Select