I have next GORM model
package entity
import (
"github.com/jinzhu/gorm"
)
type InterfaceEntity interface {
}
type User struct {
InterfaceEntity
gorm.Model
Name string
}
I try to pass GORM entity type into base crud repository. My base crud repository:
package repository
import (
"billingo/model/entity"
"fmt"
"github.com/jinzhu/gorm"
"reflect"
)
type CrudRepository struct {
*BaseRepository
}
func NewCrudRepository(db *gorm.DB) CrudRepositoryInterface {
repo := NewBaseRepository(db).(*BaseRepository)
return &CrudRepository{repo}
}
func (c CrudRepository) Find(id uint, item entity.InterfaceEntity) entity.InterfaceEntity {
fmt.Println("--- Initial")
var local entity.User
fmt.Println("--- local: ", reflect.TypeOf(local), local)
fmt.Println("--- Item: ", reflect.TypeOf(item), item)
fmt.Println("--- Values")
c.db.First(&local, id)
fmt.Println("--- local: ", reflect.TypeOf(local), local)
c.db.First(&item, id)
fmt.Println("--- Item: ", reflect.TypeOf(item), item)
return item
}
As you can see here are item and local variables in Find() method.
I pass item using next way from service:
func (c CrudService) GetItem(id uint) entity.InterfaceEntity {
var item entity.User
return c.repository.Find(id, item)
}
It seems what local and item must be equals and behavior must be equivalent.
But output is
--- Initial
--- local: entity.User {<nil> {0 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC <nil>} }
--- Item: entity.User {<nil> {0 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC <nil>} }
--- Values
--- local: entity.User {<nil> {1 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC <nil>} test 1}
--- Item: entity.User {<nil> {0 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC <nil>} }
INFO[0000] User info user="{<nil> {0 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC <nil>} }" user-id=1
(/home/mnv/go/src/billingo/model/repository/CrudRepository.go:29)
[2019-05-17 17:07:37] unsupported destination, should be slice or struct
item passed from service leads to message
unsupported destination, should be slice or struct
How to pass item correctly, I need behavior like with local?
Oh, I has fixed it.
Now repository method Find called from service with &item:
func (c CrudService) GetItem(id uint) entity.InterfaceEntity {
var item entity.User
return c.repository.Find(id, &item)
}
And repository method pass item without &:
func (c CrudRepository) Find(id uint, item entity.InterfaceEntity) entity.InterfaceEntity {
c.db.First(item, id)
return item
}
Gorm doesn't want to unmarshal the data into your empty interface type.
Even though you are passing in a struct that implements that particular interface, it still remains typed as the interface after passed. You need to cast that item interface back to your User struct.
Like item.(entity.User)