Go Generics Repository

bonus.go

// BonusRepository implements bonus.Repository
// backed by a psql database.
type BonusRepository[M GormModel[E], E any] struct {
	GormRepository[M, E]
}

type bonusRepository struct {
	db *gorm.DB
}

// NewBonusRepository returns a new BonusRepository instance.
func NewBonusRepository[M GormModel[E], E any](db *gorm.DB) *BonusRepository[M, E] {
	return &BonusRepository[M, E]{
		GormRepository[M, E](GormRepository[BonusGorm, bonus.Bonus]{
			Db: db,
		}),
	}
}

// BonusGorm represents a Bonus DTO in the psql database.
type BonusGorm struct {
	Title    string         `json:"title"`
	Type     string         `json:"type"`
	Metadata datatypes.JSON `json:"metadata"`
}

func (b BonusGorm) ToEntity() bonus.Bonus {
	//TODO implement me
	panic("implement me")
}

func (b BonusGorm) FromEntity(entity bonus.Bonus) interface{} {
	//TODO implement me
	panic("implement me")
}

func (r BonusRepository[M, E]) MyCustomMethod() {
}

repository.go

package psql

import (
	"context"
	"gorm.io/gorm"
)

type GormModel[E any] interface {
	ToEntity() E
	FromEntity(entity E) interface{}
}

func NewRepository[M GormModel[E], E any](db *gorm.DB) *GormRepository[M, E] {
	return &GormRepository[M, E]{
		Db: db,
	}
}

type GormRepository[M GormModel[E], E any] struct {
	Db *gorm.DB
}

func (r *GormRepository[M, E]) Create(
	ctx context.Context,
	entity *E,
) error {
	var m M
	model := m.FromEntity(*entity).(M)

	err := r.Db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(model).Error; err != nil {
			return err
		}

		return nil
	})

	if err != nil {
		return err
	}

	*entity = model.ToEntity()
	return nil
}