GORM provides Set, Get, InstanceSet, InstanceGet methods allow users pass values to hooks or other methods

GORM uses this for some features, like pass creating table options when migrating table.

// Add table suffix when creating tables
db.Set("gorm:table_options", "ENGINE=InnoDB").AutoMigrate(&User{})

Set / Get

Use Set / Get pass settings to hooks methods, for example:

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{})

InstanceSet / InstanceGet

Use InstanceSet / InstanceGet pass settings to current *Statement‘s hooks methods, for example:

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
  // ...
}
// 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{})