How to return a newly created record back from the database using gorm

In Go, when using the GORM library to interact with a database, retrieving the newly created record after insertion can be achieved through several steps. Below are the specific steps and code examples.

Step 1: Define the Model

First, you need to define a model that maps to a database table. Suppose we have a table called User, and the model might look like this:

go
type User struct {
    ID        uint   `gorm:"primary_key"`
    Name      string
    Email     string
    Age       int
}

Step 2: Create the Record

Using GORM's Create method, you can insert a new record. During this process, GORM automatically updates the provided model instance with the details of the newly created record, such as the ID generated by the database.

go
func CreateUser(db *gorm.DB, user *User) error {
    if err := db.Create(user).Error; err != nil {
        return err
    }
    return nil
}

In the above CreateUser function, the user object is updated after being passed to the Create method. For example, if the database ID is auto-incremented, user.ID will be set to the ID of the newly created record.

Step 3: Return and Use the Newly Created Record

After creating the record, the user object already contains all new database fields, including any database-generated values (such as ID, timestamps, etc.). You can continue using this user object or return it for further processing.

go
db := // Assume this is a configured and initialized *gorm.DB instance
newUser := User{Name: "Alice", Email: "alice@example.com", Age: 30}
err := CreateUser(db, &newUser)
if err != nil {
    log.Fatalf("Failed to create user: %v", err)
}
fmt.Printf("New user created with ID: %d", newUser.ID)

In this example, we create a new User object and save it to the database using the CreateUser function. The function internally calls GORM's Create method, which updates the newUser object to include all new information from the database, such as the newly assigned ID.

By doing this, you can easily retrieve and use the latest state of the record after creation, which is particularly useful for scenarios requiring further processing. For instance, you might need to create related records or log the new user ID based on the newly created record.