[英]Using transaction and simple DB connection in the same struct because of this pattern what can I do?
我發現了一個使用 Clean Architecture 方法在 Repositories 之間進行交易的很好的例子。
這家伙正在使用Gorm 。
Gorm 對數據庫連接和事務具有相同的類型,例如:
var db *gorm.DB
var tx *gorm.DB
我是go-pg
的粉絲。 但是這里的類型是不同的(也許更好),例如:
var db *pg.DB
var tx *pg.Tx
當然錯誤是: Cannot use 'tx' (type *Tx) as type *pg.DB
一個小復制:
package main
import (
"github.com/go-pg/pg/v10"
)
type Player struct {
ID int
Name string
}
type PlayerRepo struct {
db *pg.DB
teamRepo *TeamRepo
}
type TeamRepo struct {
db *pg.DB
}
func NewPlayerRepo(db *pg.DB) *PlayerRepo {
return &PlayerRepo{
db: db,
teamRepo: NewTeamRepo(db),
}
}
func NewTeamRepo(db *pg.DB) *TeamRepo {
return &TeamRepo{db: db}
}
func (r *PlayerRepo) Find(id int) (*Player, error) {
var player Player
err := r.db.Model(&player).Where("id = ?", id).Select()
if err != nil {
return nil, err
}
return &player, nil
}
func (r *PlayerRepo) All() ([]*Player, error) {
// Long code
return nil, nil
}
func (r *PlayerRepo) Insert() (*Player, error) {
// Long code
return nil, nil
}
func (r *PlayerRepo) Update() (*Player, error) {
// Long code
return nil, nil
}
func (r *PlayerRepo) Delete() (*Player, error) {
// Long code
return nil, nil
}
func (r *PlayerRepo) WithTransaction(txFunc func(*PlayerRepo) error) (err error) {
tx, _ := r.db.Begin()
manager := NewPlayerRepo(tx) // <<<--- here the problem! tx is not good here, it's `pg.Tx` not `pg.DB`
err = txFunc(manager)
return
}
我能做些什么來解決這個問題?
提前致謝。 ❤️
您可以定義一個已經由兩者隱式實現的接口:
type DB interface {
Begin() (*Tx, error)
Close() error
Context() context.Context
CopyFrom(r io.Reader, query interface{}, params ...interface{}) (res Result, err error)
CopyTo(w io.Writer, query interface{}, params ...interface{}) (res Result, err error)
Exec(query interface{}, params ...interface{}) (Result, error)
ExecContext(c context.Context, query interface{}, params ...interface{}) (Result, error)
ExecOne(query interface{}, params ...interface{}) (Result, error)
ExecOneContext(c context.Context, query interface{}, params ...interface{}) (Result, error)
Formatter() orm.QueryFormatter
Model(model ...interface{}) *orm.Query
ModelContext(c context.Context, model ...interface{}) *orm.Query
Prepare(q string) (*Stmt, error)
Query(model interface{}, query interface{}, params ...interface{}) (Result, error)
QueryContext(c context.Context, model interface{}, query interface{}, params ...interface{}) (Result, error)
QueryOne(model interface{}, query interface{}, params ...interface{}) (Result, error)
QueryOneContext(c context.Context, model interface{}, query interface{}, params ...interface{}) (Result, error)
RunInTransaction(ctx context.Context, fn func(*Tx) error) error
}
注意:我只知道方法名稱匹配,我沒有費心檢查簽名是否也匹配,如果不匹配,您需要相應地編輯界面。
您可以添加一個簡單的“編譯器檢查”:
var _ DB = (*pg.DB)(nil)
var _ DB = (*pg.Tx)(nil)
然后您可以將PlayerRepo.db
字段的類型從*pg.DB
為新的DB
接口。
type PlayerRepo struct {
db DB
teamRepo *TeamRepo
}
type TeamRepo struct {
db DB
}
func NewPlayerRepo(db DB) *PlayerRepo {
return &PlayerRepo{
db: db,
teamRepo: NewTeamRepo(db),
}
}
func NewTeamRepo(db DB) *TeamRepo {
return &TeamRepo{db: db}
}
func (r *PlayerRepo) WithTransaction(txFunc func(*PlayerRepo) error) (err error) {
tx, err := r.db.Begin()
if err != nil {
return err
}
defer func() {
// rollback if err; commit if no err
}()
manager := NewPlayerRepo(tx)
err = txFunc(manager)
return
}
如果您的 repo 類型需要能夠調用pg.DB
和pg.Tx
不通用的一些方法,因此沒有由新的DB
接口定義,那么,一種方法是保留原始類型這樣的使用,例如:
type PlayerRepo struct {
db DB
pg *pg.DB
teamRepo *TeamRepo
}
type TeamRepo struct {
db DB
pg *pg.DB
}
func NewPlayerRepo(db DB, pg *pg.DB) *PlayerRepo {
return &PlayerRepo{
db: db,
pg: pg,
teamRepo: NewTeamRepo(db, pg),
}
}
func NewTeamRepo(db DB, pg *pg.DB) *TeamRepo {
return &TeamRepo{db: db, pg: pg}
}
func (r *PlayerRepo) WithTransaction(txFunc func(*PlayerRepo) error) (err error) {
tx, err := r.db.Begin()
if err != nil {
return err
}
defer func() {
// rollback if err; commit if no err
}()
manager := NewPlayerRepo(tx, r.pg)
err = txFunc(manager)
return
}
請注意,如果您決定使用orm.DB
,這是合理的,但它缺少您需要的一些方法並且已經由pg.DB
和pg.Tx
,那么您可以將orm.DB
嵌入到您的自定義接口並僅添加那些缺少的方法。
type DB interface {
Begin() (*Tx, error)
orm.DB
}
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