// Append
	toy := Toy{Name: "toy-has-one-append"}

	if err := DB.Model(&pet2).Association("Toy").Append(&toy); err != nil {
		t.Fatalf("Error happened when append toy, got %v", err)
	}

	if toy.ID == 0 {
		t.Fatalf("Toy's ID should be created")
	}

	pet.Toy = toy
	CheckPet(t, pet2, pet)

	AssertAssociationCount(t, pet, "Toy", 1, "AfterAppend")

	// Replace

	Active    bool
}

type Account struct {
	gorm.Model
	UserID sql.NullInt64
	Number string
}

type Pet struct {
	gorm.Model
	UserID *uint
	Name   string
	Toy    Toy `gorm:"polymorphic:Owner;"`
}

type Toy struct {
	gorm.Model
	Name      string
	OwnerID   string
	OwnerType string
}

type Tools struct {
	gorm.Model
	Name     string
	CustomID string
	Type     string
}

	AssertObjEqual(t, pet, expect, "ID", "CreatedAt", "UpdatedAt", "DeletedAt", "UserID", "Name")

	AssertObjEqual(t, pet.Toy, expect.Toy, "ID", "CreatedAt", "UpdatedAt", "DeletedAt", "Name", "OwnerID", "OwnerType")

	if expect.Toy.Name != "" && expect.Toy.OwnerType != "pets" {
		t.Errorf("toys's OwnerType, expect: %v, got %v", "pets", expect.Toy.OwnerType)
	}
}

func CheckUserUnscoped(t *testing.T, user User, expect User) {

			t.Fatalf("errors happened when create: %v", err)
		}

		pet.Toy = Toy{Name: "Update-HasOneAssociation-Polymorphic"}

		if err := DB.Save(&pet).Error; err != nil {
			t.Fatalf("errors happened when create: %v", err)
		}

		var pet2 Pet
		DB.Preload("Toy").Find(&pet2, "id = ?", pet.ID)
		CheckPet(t, pet2, pet)

		pet.Toy.Name += "new"
		if err := DB.Save(&pet).Error; err != nil {

		t.Errorf("Hamster's preferred toy failed to preload")
	}

	if hamster2.OtherToy.ID != hamster.OtherToy.ID || hamster2.OtherToy.Name != hamster.OtherToy.Name {
		t.Errorf("Hamster's other toy failed to preload")
	}

	// clear to omit Toy.ID in count
	hamster2.PreferredToy = Toy{}
	hamster2.OtherToy = Toy{}

	if DB.Model(&hamster2).Association("PreferredToy").Count() != 1 {

	t.Run("Polymorphic", func(t *testing.T) {
		user := *GetUser("update-has-many", Config{})

		if err := DB.Create(&user).Error; err != nil {
			t.Fatalf("errors happened when create: %v", err)
		}

		user.Toys = []Toy{{Name: "toy1"}, {Name: "toy2"}}
		if err := DB.Save(&user).Error; err != nil {
			t.Fatalf("errors happened when update: %v", err)
		}

		var user2 User
		DB.Preload("Toys").Find(&user2, "id = ?", user.ID)

	"gorm.io/gorm/utils/tests"
)

type User struct {
	*gorm.Model
	Name      *string
	Age       *uint
	Birthday  *time.Time
	Account   *tests.Account
	Pets      []*tests.Pet
	Toys      []*tests.Toy `gorm:"polymorphic:Owner"`
	CompanyID *int
	Company   *tests.Company
	ManagerID *uint
	Manager   *User
	Team      []*User           `gorm:"foreignkey:ManagerID"`
	Languages []*tests.Language `gorm:"many2many:UserSpeak"`

```json
{
    "reason": <string>
}
```

The reason message is returned to the client.

## Example Plugin Implementation

	} else if debug == "false" {
		db.Logger = db.Logger.LogMode(logger.Silent)
	}

	return
}

func RunMigrations() {
	var err error
	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}, &Order{}, &Parent{}, &Child{}, &Tools{}}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(allModels), func(i, j int) { allModels[i], allModels[j] = allModels[j], allModels[i] })

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class

!!! tip
    This is a toy example to demonstrate how it works, if you need Gzip support, you can use the provided [`GzipMiddleware`](../advanced/middleware.md#gzipmiddleware){.internal-link target=_blank}.