# Models · GORM Guide
Gorm has defined struct gorm.Model, which could be embeded in your models, it will add fields ID, CreatedAt, UpdatedAt, DeletedAt to your model

# Models

- Model Defination
- Conventions & Overriding Conventions
  - `gorm.Model` struct
  - Table name is the pluralized version of struct name
  - Column name is the snake case of field's name
  - Field `ID` as primary key
  - Field `CreatedAt` used to store record's created time
  - Use `UpdatedAt` used to store record's updated time
  - Use `DeletedAt` to store record's deleted time if field exists

## Model Defination

    type User struct {
      gorm.Model
        Birthday     time.Time
        Age          int
        Name         string  `sql:"size:255"` // Default size for string is 255, you could reset it with this tag
        Num          int     `sql:"AUTO_INCREMENT"`
        IgnoreMe     int `sql:"-"`   // Ignore this field
    }

## Conventions & Overriding Conventions

### `gorm.Model` struct

Gorm has defined struct `gorm.Model`, which could be embeded in your models, it will add fields `ID`, `CreatedAt`, `UpdatedAt`, `DeletedAt` to your model

    // Model's definition
    type Model struct {
      ID        uint `gorm:"primary_key"`
      CreatedAt time.Time
      UpdatedAt time.Time
      DeletedAt *time.Time
    }

### 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
    type (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

### 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`
    }

    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` is the default primary key for `User`
      Name string
    }

    // your could also use tag `primary_key` to set other field as 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.

    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 delete the record from database, but will set field `DeletedAt`'s value to current time.