Scopes

作用域允许你复用通用的逻辑,这种共享逻辑需要定义为类型func(*gorm.DB) *gorm.DB

查询

Scope 查询示例:

func AmountGreaterThan1000(db *gorm.DB) *gorm.DB {
return db.Where("amount > ?", 1000)
}

func PaidWithCreditCard(db *gorm.DB) *gorm.DB {
return db.Where("pay_mode_sign = ?", "C")
}

func PaidWithCod(db *gorm.DB) *gorm.DB {
return db.Where("pay_mode_sign = ?", "C")
}

func OrderStatus(status []string) func (db *gorm.DB) *gorm.DB {
return func (db *gorm.DB) *gorm.DB {
return db.Where("status IN (?)", status)
}
}

db.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find(&orders)
// 查找所有金额大于 1000 的信用卡订单

db.Scopes(AmountGreaterThan1000, PaidWithCod).Find(&orders)
// 查找所有金额大于 1000 的 COD 订单

db.Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find(&orders)
// 查找所有金额大于1000 的已付款或已发货订单

分页

func Paginate(r *http.Request) func(db *gorm.DB) *gorm.DB {
return func (db *gorm.DB) *gorm.DB {
page, _ := strconv.Atoi(r.Query("page"))
if page == 0 {
page = 1
}

pageSize, _ := strconv.Atoi(r.Query("page_size"))
switch {
case pageSize > 100:
pageSize = 100
case pageSize <= 0:
pageSize = 10
}

offset := (page - 1) * pageSize
return db.Offset(offset).Limit(pageSize)
}
}

db.Scopes(Paginate(r)).Find(&users)
db.Scopes(Paginate(r)).Find(&articles)

更新

Scope 更新、删除示例:

func CurOrganization(r *http.Request) func(db *gorm.DB) *gorm.DB {
return func (db *gorm.DB) *gorm.DB {
org := r.Query("org")

if org != "" {
var organization Organization
if db.Session(&Session{}).First(&organization, "name = ?", org).Error == nil {
return db.Where("org_id = ?", organization.ID)
}
}

db.AddError("invalid organization")
return db
}
}

db.Model(&article).Scopes(CurOrganization(r)).Update("Name", "name 1")
// UPDATE articles SET name = "name 1" WHERE org_id = 111
db.Scopes(CurOrganization(r)).Delete(&Article{})
// DELETE FROM articles WHERE org_id = 111

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