Estos **type hints** son una nueva sintaxis, desde Python 3.6+, que permite declarar el <abbr title="por ejemplo: str, int, float, bool">tipo</abbr> de una variable.

Usando las declaraciones de tipos para tus variables, los editores y otras herramientas pueden proveerte un soporte mejor.

	"gorm.io/gorm"
	"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"`

	type (
		Level0 struct {
			ID       uint
			Value    string
			Level1ID uint
		}
		Level1 struct {
			ID         uint
			Value      string
			Level2ID   *uint
			Level2_1ID *uint
			Level0s    []Level0 `json:",omitempty"`
		}
		Level2 struct {
			ID       uint
			Level1s  []Level1
			Level3ID uint
		}
		Level2_1 struct {
			ID       uint
			Level1s  []Level1 `json:",omitempty"`

		Name      string
		UserRefer uint
	}

	type User struct {
		gorm.Model
		Profiles  []Profile `gorm:"many2many:user_profiles;ForeignKey:Refer;JoinForeignKey:UserReferID;References:UserRefer;JoinReferences:ProfileRefer"`
		Profiles2 []Profile `gorm:"many2many:user_profiles2;ForeignKey:refer;JoinForeignKey:user_refer_id;References:user_refer;JoinReferences:profile_refer"`
		Refer     uint
	}

func (z *scanStatus) DecodeMsg(dc *msgp.Reader) (err error) {
	{
		var zb0001 uint8
		zb0001, err = dc.ReadUint8()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		(*z) = scanStatus(zb0001)
	}
	return
}

// EncodeMsg implements msgp.Encodable
func (z scanStatus) EncodeMsg(en *msgp.Writer) (err error) {
	err = en.WriteUint8(uint8(z))
	if err != nil {
		err = msgp.WrapError(err)
		return
	}

	{
		var zb0001 uint8
		zb0001, err = dc.ReadUint8()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		(*z) = ResponseCode(zb0001)
	}
	return
}

// EncodeMsg implements msgp.Encodable
func (z ResponseCode) EncodeMsg(en *msgp.Writer) (err error) {
	err = en.WriteUint8(uint8(z))
	if err != nil {
		err = msgp.WrapError(err)
		return
	}

  public void testImmutableEnumSet() {
    Set<SomeEnum> units = Sets.immutableEnumSet(SomeEnum.D, SomeEnum.B);

    assertThat(units).containsExactly(SomeEnum.B, SomeEnum.D).inOrder();
    assertThrows(UnsupportedOperationException.class, () -> units.remove(SomeEnum.B));
    assertThrows(UnsupportedOperationException.class, () -> units.add(SomeEnum.C));
  }

  public void testToImmutableEnumSet() {

	}
}

func TestForeignKeyConstraints(t *testing.T) {
	tidbSkip(t, "not support the foreign key feature")

	type Profile struct {
		ID       uint
		Name     string
		MemberID uint
	}

	type Member struct {
		ID      uint
		Refer   uint `gorm:"uniqueIndex"`
		Name    string
		Profile Profile `gorm:"Constraint:OnUpdate:CASCADE,OnDelete:CASCADE;FOREIGNKEY:MemberID;References:Refer"`
	}

func TestCompositePrimaryKeyWithAutoIncrement(t *testing.T) {
	type Product struct {
		ProductID    uint `gorm:"primaryKey;autoIncrement"`
		LanguageCode uint `gorm:"primaryKey"`
		Code         string
		Name         string
	}
	type ProductNonAutoIncrement struct {
		ProductID    uint `gorm:"primaryKey;autoIncrement:false"`
		LanguageCode uint `gorm:"primaryKey"`
		Code         string
		Name         string
	}

Daarnaast betekent het ook dat je code zeer verenigbaar zal zijn met veel andere Python-hulpmiddelen en -pakketten. 🚀

///

## Type hints in **FastAPI**

**FastAPI** maakt gebruik van type hints om verschillende dingen te doen.

Met **FastAPI** declareer je parameters met type hints en krijg je:

* **Editor ondersteuning**.
* **Type checks**.

...en **FastAPI** gebruikt dezelfde declaraties om: