How to do a many-to-many query - go

Question

I'm trying to understand how to use GORM to make query on items with many2many relations but I'm really lost.
I've got the following database model:
type Asset struct {
gorm.Model
Id uint `gorm:"primaryKey"`
MachineUID string `gorm:"type:varchar(128)" json:"machine_uid"`
AssetToken string `gorm:"uniqueIndex;type:varchar(128)"`
CommandQueries []*CommandQuery `gorm:"many2many:command_asset;"`
}
type CommandQuery struct {
gorm.Model
Id uint `gorm:"primaryKey"`
UUID string `gorm:"type:varchar(128)" json:"uuid"`
CmdType int `json:"cmdtype"`
CmdArgs string `gorm:"type:varchar(128)" json:"cmdargs"`
Assets *[]Asset `gorm:"many2many:command_asset;"`
Active bool
}
First, i'm successfully trying to retrieve an asset from a token with something like this:
token := "test-token"
var result Asset
db.Where("asset_token = ?", token).First(&result)
if result.Id == 0 {
return fmt.Errorf("Asset cannot be found in database")
}
But fom this returned struct, i would like to retrive all CommandQuery objects where:
this asset is in CommandQuery.assets
Where CommandQuery.active = true
I tried many things but nothing works, any help would be appreciated.

Answer 1

If I understood correctly, you want to load a slice of CommandQuery objects, and these objects should contain only assets where asset_token should be equal to the token you passed. Also, return only CommanQuery objects that have active=true.
If this is the case, it can be done like this:
token := "test-token"
var list []CommandQuery{}
tx := db.Preload("Assets", func (gdb *gorm.DB) *gorm.DB{
return gdb.Where("asset_token = ?", token)
}).
Where("active = ?", true).Find(&list)
if tx.Error == nil {
return nil, tx.Error
}
return *list, nil
In short, custom preloading is used to load assets into command query objects.