范围 Scopes
原文：https://gorm.io/docs/scopes.html
Scopes allow you to re-use commonly used logic, the shared logic needs to be defined as type func(*gorm.DB) *gorm.DB
范围允许你重用常用逻辑，共享逻辑需要定义为类型 func(*gorm.DB) *gorm.DB
查询 Query
Scope examples for querying
范围示例用于查询
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
| func AmountGreaterThan1000(db *gorm.DB) *gorm.DB {
return db.Where("amount > ?", 1000)
}
func PaidWithCreditCard(db *gorm.DB) *gorm.DB {
return db.Where("pay_mode = ?", "card")
}
func PaidWithCod(db *gorm.DB) *gorm.DB {
return db.Where("pay_mode = ?", "cod")
}
func OrderStatus(status []string) func (db *gorm.DB) *gorm.DB {
return func (db *gorm.DB) *gorm.DB {
return db.Scopes(AmountGreaterThan1000).Where("status IN (?)", status)
}
}
db.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find(&orders)
// 查找所有信用卡订单且金额大于1000 Find all credit card orders and amount greater than 1000
db.Scopes(AmountGreaterThan1000, PaidWithCod).Find(&orders)
// 查找所有COD订单且金额大于1000 Find all COD orders and amount greater than 1000
db.Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find(&orders)
// 查找所有已支付、已发货的订单且金额大于1000 Find all paid, shipped orders that amount greater than 1000
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
| func Paginate(r *http.Request) func(db *gorm.DB) *gorm.DB {
return func (db *gorm.DB) *gorm.DB {
q := r.URL.Query()
page, _ := strconv.Atoi(q.Get("page"))
if page <= 0 {
page = 1
}
pageSize, _ := strconv.Atoi(q.Get("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)
|
动态表名 Dynamically Table
Use Scopes to dynamically set the query Table
使用 Scopes 动态设置查询表名
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
| func TableOfYear(user *User, year int) func(db *gorm.DB) *gorm.DB {
return func(db *gorm.DB) *gorm.DB {
tableName := user.TableName() + strconv.Itoa(year)
return db.Table(tableName)
}
}
DB.Scopes(TableOfYear(user, 2019)).Find(&users)
// SELECT * FROM users_2019;
DB.Scopes(TableOfYear(user, 2020)).Find(&users)
// SELECT * FROM users_2020;
// 来自不同数据库的表 Table form different database
func TableOfOrg(user *User, dbName string) func(db *gorm.DB) *gorm.DB {
return func(db *gorm.DB) *gorm.DB {
tableName := dbName + "." + user.TableName()
return db.Table(tableName)
}
}
DB.Scopes(TableOfOrg(user, "org1")).Find(&users)
// SELECT * FROM org1.users;
DB.Scopes(TableOfOrg(user, "org2")).Find(&users)
// SELECT * FROM org2.users;
|
更新 Updates
Scope examples for updating/deleting
更新/删除的范围示例
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
| 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
|