return ErrUnknownHandler
	}
	s := strings.Join(subroute, "/")
	if debugPrint {
		fmt.Println("RegisterSingleHandler: ", id.String(), "subroute:", s)
	}

	if len(subroute) == 0 {
		if m.handlers.hasAny(id) && !id.isTestHandler() {
			return fmt.Errorf("handler %v: %w", id.String(), ErrHandlerAlreadyExists)
		}

		m.handlers.single[id] = h
		return nil
	}
	subID := makeSubHandlerID(id, s)

func (h *handlers) init() {
	h.subSingle = make(map[subHandlerID]SingleHandlerFn)
	h.subStateless = make(map[subHandlerID]*StatelessHandler)
	h.subStreams = make(map[subHandlerID]*StreamHandler)
}

func (h *handlers) hasAny(id HandlerID) bool {
	if !id.valid() {
		return false
	}
	return h.single[id] != nil || h.stateless[id] != nil || h.streams[id] != nil
}

func (h *handlers) hasSubhandler(id subHandlerID) bool {

		UserRefer uint
	}

	type User struct {
		gorm.Model
		Profile Profile `gorm:"ForeignKey:UserRefer"`
	}

	checkStructRelation(t, &User{}, Relation{
		Name: "Profile", Type: schema.HasOne, Schema: "User", FieldSchema: "Profile",
		References: []Reference{{"ID", "User", "UserRefer", "Profile", "", true}},
	})
}

func TestHasOneOverrideReferences(t *testing.T) {
	type Profile struct {
		gorm.Model

		case reflect.Struct:
			relation.Type = HasOne
		case reflect.Slice:
			relation.Type = HasMany
		}
	}

	if schema.err == nil {
		schema.setRelation(relation)
		switch relation.Type {
		case HasOne:
			schema.Relationships.HasOne = append(schema.Relationships.HasOne, relation)
		case HasMany:
			schema.Relationships.HasMany = append(schema.Relationships.HasMany, relation)
		case BelongsTo:

			}
			if association.Unscope && oldBelongsToExpr != nil {
				association.Error = association.DB.Model(nil).Where(oldBelongsToExpr).Delete(reflect.New(rel.FieldSchema.ModelType).Interface()).Error
			}
		case schema.HasOne, schema.HasMany:
			var (
				primaryFields []*schema.Field
				foreignKeys   []string
				updateMap     = map[string]interface{}{}

	relations := []Relation{
		{
			Name: "Account", Type: schema.HasOne, Schema: "User", FieldSchema: "Account",
			References: []Reference{{"ID", "User", "UserID", "Account", "", true}},
		},
		{
			Name: "Pets", Type: schema.HasMany, Schema: "User", FieldSchema: "Pet",
			References: []Reference{{"ID", "User", "UserID", "Pet", "", true}},
		},
		{
			Name: "Toys", Type: schema.HasMany, Schema: "User", FieldSchema: "Toy",

			if !v {
				continue
			}

			rel, ok := db.Statement.Schema.Relationships.Relations[column]
			if !ok {
				continue
			}

			switch rel.Type {
			case schema.HasOne, schema.HasMany:
				queryConds := rel.ToQueryConditions(db.Statement.Context, db.Statement.ReflectValue)
				modelValue := reflect.New(rel.FieldSchema.ModelType).Interface()
				tx := db.Session(&gorm.Session{NewDB: true}).Model(modelValue)

		if db.Error == nil && db.Statement.Schema != nil {
			selectColumns, restricted := db.Statement.SelectAndOmitColumns(create, !create)

			// Save Has One associations
			for _, rel := range db.Statement.Schema.Relationships.HasOne {
				if v, ok := selectColumns[rel.Name]; (ok && !v) || (!ok && restricted) {
					continue
				}

				switch db.Statement.ReflectValue.Kind() {
				case reflect.Slice, reflect.Array:
					var (

		t.Errorf("account's number should not be saved")
	}
}

func TestHasOneAssociationForSlice(t *testing.T) {
	users := []User{
		*GetUser("slice-hasone-1", Config{Account: true}),
		*GetUser("slice-hasone-2", Config{Account: false}),
		*GetUser("slice-hasone-3", Config{Account: true}),
	}

	DB.Create(&users)

	// Count
	AssertAssociationCount(t, users, "Account", 2, "")

	// Find

	if uni, ok := uniqueConstraints[name]; ok {
		return &uni, stmt.Table
	}

	getTable := func(rel *schema.Relationship) string {
		switch rel.Type {
		case schema.HasOne, schema.HasMany:
			return rel.FieldSchema.Table
		case schema.Many2Many:
			return rel.JoinTable.Table
		}
		return stmt.Table
	}

	for _, rel := range stmt.Schema.Relationships.Relations {