Models

Model Definition

type User struct {
    gorm.Model
    Birthday     time.Time
    Age          int
    Name         string  `gorm:"size:255"` // Default size for string is 255, reset it with this tag
    Num          int     `gorm:"AUTO_INCREMENT"`
    CreditCard        CreditCard      // One-To-One relationship (has one - use CreditCard's UserID as foreign key)
    Emails            []Email         // One-To-Many relationship (has many - use Email's UserID as foreign key)
    BillingAddress    Address         // One-To-One relationship (belongs to - use BillingAddressID as foreign key)
    BillingAddressID  sql.NullInt64
    ShippingAddress   Address         // One-To-One relationship (belongs to - use ShippingAddressID as foreign key)
    ShippingAddressID int
    IgnoreMe          int `gorm:"-"`   // Ignore this field
    Languages         []Language `gorm:"many2many:user_languages;"` // Many-To-Many relationship, 'user_languages' is join table
}
type Email struct {
    ID      int
    UserID  int     `gorm:"index"` // Foreign key (belongs to), tag `index` will create index for this column
    Email   string  `gorm:"type:varchar(100);unique_index"` // `type` set sql type, `unique_index` will create unique index for this column
    Subscribed bool
}
type Address struct {
    ID       int
    Address1 string         `gorm:"not null;unique"` // Set field as not nullable and unique
    Address2 string         `gorm:"type:varchar(100);unique"`
    Post     sql.NullString `gorm:"not null"`
}
type Language struct {
    ID   int
    Name string `gorm:"index:idx_name_code"` // Create index with name, and will create combined index if find other fields defined same name
    Code string `gorm:"index:idx_name_code"` // `unique_index` also works
}
type CreditCard struct {
    gorm.Model
    UserID  uint
    Number  string
}

Conventions

gorm.Model struct

Base model definition gorm.Model, including fields ID, CreatedAt, UpdatedAt, DeletedAt, you could embed it in your model, or only write those fields you want

// Base Model's definition
type Model struct {
  ID        uint `gorm:"primary_key"`
  CreatedAt time.Time
  UpdatedAt time.Time
  DeletedAt *time.Time
}
// Add fields `ID`, `CreatedAt`, `UpdatedAt`, `DeletedAt`
type User struct {
  gorm.Model
  Name string
}
// Only need field `ID`, `CreatedAt`
type User struct {
  ID        uint
  CreatedAt time.Time
  Name      string
}

Table name is the pluralized version of struct name

type User struct {} // default table name is `users`
// set User's table name to be `profiles`
func (User) TableName() string {
  return "profiles"
}
func (u User) TableName() string {
    if u.Role == "admin" {
        return "admin_users"
    } else {
        return "users"
    }
}
// Disable table name's pluralization globally
db.SingularTable(true) // if set this to true, `User`'s default table name will be `user`, table name setted with `TableName` won't be affected

Change default tablenames

You can apply any rules on the default table name by defining the DefaultTableNameHandler

gorm.DefaultTableNameHandler = func (db *gorm.DB, defaultTableName string) string  {
    return "prefix_" + defaultTableName;
}

Column name is the snake case of field’s name

type User struct {
  ID uint             // column name will be `id`
  Name string         // column name will be `name`
  Birthday time.Time  // column name will be `birthday`
  CreatedAt time.Time // column name will be `created_at`
}
// Overriding Column Name
type Animal struct {
    AnimalId    int64     `gorm:"column:beast_id"`         // set column name to `beast_id`
    Birthday    time.Time `gorm:"column:day_of_the_beast"` // set column name to `day_of_the_beast`
    Age         int64     `gorm:"column:age_of_the_beast"` // set column name to `age_of_the_beast`
}

Field ID as primary key

type User struct {
  ID   uint  // field named `ID` will be the default primary field
  Name string
}
// Set a field to be primary field with tag `primary_key`
type Animal struct {
  AnimalId int64 `gorm:"primary_key"` // set AnimalId to be primary key
  Name     string
  Age      int64
}

Field CreatedAt used to store record’s created time

Create records having CreatedAt field will set it to current time.

db.Create(&user) // will set `CreatedAt` to current time
// To change its value, you could use `Update`
db.Model(&user).Update("CreatedAt", time.Now())

Use UpdatedAt used to store record’s updated time

Save records having UpdatedAt field will set it to current time.

// Whenever one or more `user` fields are edited using Save() or Update(), `UpdatedAt` will be set to current time
db.Save(&user) // will set `UpdatedAt` to current time
db.Model(&user).Update("name", "jinzhu") // will set `UpdatedAt` to current time

Use DeletedAt to store record’s deleted time if field exists

Delete records having DeletedAt field, it won’t be deleted from database, but only set field DeletedAt‘s value to current time, and the record is not findable when querying, refer Soft Delete