设置
原文：https://gorm.io/docs/settings.html
GORM provides Set, Get, InstanceSet, InstanceGet methods allow users pass values to hooks or other methods
GORM提供了Set、Get、InstanceSet和InstanceGet方法，允许用户向钩子（hooks）或其他方法传递值。
GORM uses this for some features, like pass creating table options when migrating table.
GORM在迁移表时使用这些功能，例如传递创建表选项。
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| // 在创建表时添加表后缀 Add table suffix when creating tables
db.Set("gorm:table_options", "ENGINE=InnoDB").AutoMigrate(&User{})
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Set / Get
Use Set / Get pass settings to hooks methods, for example:
使用Set / Get将设置传递给钩子方法，例如：
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| type User struct {
gorm.Model
CreditCard CreditCard
// ...
}
func (u *User) BeforeCreate(tx *gorm.DB) error {
myValue, ok := tx.Get("my_value")
// ok => true
// myValue => 123
}
type CreditCard struct {
gorm.Model
// ...
}
func (card *CreditCard) BeforeCreate(tx *gorm.DB) error {
myValue, ok := tx.Get("my_value")
// ok => true
// myValue => 123
}
myValue := 123
db.Set("my_value", myValue).Create(&User{})
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InstanceSet / InstanceGet
Use InstanceSet / InstanceGet pass settings to current *Statement‘s hooks methods, for example:
使用InstanceSet / InstanceGet将设置传递给当前*Statement的钩子方法，例如：
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| type User struct {
gorm.Model
CreditCard CreditCard
// ...
}
func (u *User) BeforeCreate(tx *gorm.DB) error {
myValue, ok := tx.InstanceGet("my_value")
// ok => true
// myValue => 123
}
type CreditCard struct {
gorm.Model
// ...
}
// 当创建关联时，GORM会创建一个新`*Statement`，因此无法读取其他实例的设置 When creating associations, GORM creates a new `*Statement`, so can't read other instance's settings
func (card *CreditCard) BeforeCreate(tx *gorm.DB) error {
myValue, ok := tx.InstanceGet("my_value")
// ok => false
// myValue => nil
}
myValue := 123
db.InstanceSet("my_value", myValue).Create(&User{})
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