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Hooks

pages/ar_SA/docs/hooks.md

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Object Life Cycle

Hooks are functions that are called before or after creation/querying/updating/deletion.

If you have defined specified methods for a model, it will be called automatically when creating, updating, querying, deleting, and if any callback returns an error, GORM will stop future operations and rollback current transaction.

The type of hook methods should be func(*gorm.DB) error

Hooks

Creating an object

Available hooks for creating

go
// begin transaction
BeforeSave
BeforeCreate
// save before associations
// insert into database
// save after associations
AfterCreate
AfterSave
// commit or rollback transaction

Code Example:

go
func (u *User) BeforeCreate(tx *gorm.DB) error {
  // Modify current operation through tx. Statement, e.g:
  tx. Select("Name", "Age")
  tx. AddClause(clause. OnConflict{DoNothing: true})

  // tx is new session mode without the `WithConditions` option
  // operations based on it will run inside same transaction but without any current conditions
  var role Role
  err := tx. First(&role, "name = ?", user. Role). Error
  // SELECT * FROM roles WHERE name = "admin"
  // ... return err
}

{% note warn %} NOTE Save/Delete operations in GORM are running in transactions by default, so changes made in that transaction are not visible until it is committed, if you return any error in your hooks, the change will be rollbacked {% endnote %}

go
func (u *User) BeforeCreate(tx *gorm.DB) error {
  // Modify current operation through tx. Statement, e.g:
  tx. Select("Name", "Age")
  tx. AddClause(clause. OnConflict{DoNothing: true})

  // tx is new session mode without the `WithConditions` option
  // operations based on it will run inside same transaction but without any current conditions
  var role Role
  err := tx. First(&role, "name = ?", user. Role).

Updating an object

Available hooks for updating

go
// begin transaction
BeforeSave
BeforeUpdate
// save before associations
// update database
// save after associations
AfterUpdate
AfterSave
// commit or rollback transaction

Code Example:

go
func (u *User) BeforeCreate(tx *gorm.DB) error {
  // Modify current operation through tx. Statement, e.g:
  tx. Select("Name", "Age")
  tx. AddClause(clause. OnConflict{DoNothing: true})

  // tx is new session mode without the `WithConditions` option
  // operations based on it will run inside same transaction but without any current conditions
  var role Role
  err := tx. First(&role, "name = ?", user.

Deleting an object

Available hooks for deleting

go
// begin transaction
BeforeDelete
// delete from database
AfterDelete
// commit or rollback transaction

Code Example:

go
func (u *User) BeforeCreate(tx *gorm.DB) error {
  // Modify current operation through tx. Statement, e.g:
  tx. Select("Name", "Age")
  tx. AddClause(clause. OnConflict{DoNothing: true})

  // tx is new session mode without the `WithConditions` option
  // operations based on it will run inside same transaction but without any current conditions
  var role Role
  err := tx. First(&role, "name = ?", user.

Querying an object

Available hooks for querying

go
// load data from database
// Preloading (eager loading)
AfterFind

Code Example:

go
func (u *User) AfterFind(tx *gorm.DB) (err error) {
  if u. MemberShip == "" {
    u. MemberShip = "user"
  }
  return
}

Modify current operation

go
func (u *User) BeforeCreate(tx *gorm.DB) error {
  // Modify current operation through tx.Statement, e.g:
  tx.Statement.Select("Name", "Age")
  tx.Statement.AddClause(clause.OnConflict{DoNothing: true})

  // tx is new session mode with the `NewDB` option
  // operations based on it will run inside same transaction but without any current conditions
  var role Role
  err := tx.First(&role, "name = ?", user.Role).Error
  // SELECT * FROM roles WHERE name = "admin"
  // ...
  return err
}