Golang和GORM。 如何正确地将模型类型传递给方法？

Question

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?

Answer 1

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
}