Mastering Enums in GORM: A Step-by-Step Guide for Go Developers

GORM Enum Introduction

GORM is a popular Go ORM that maps structs to database tables and provides CRUD interfaces. Enums allow a variable to take a fixed set of values. This article shows how to add enums to GORM models.

Step 1: Define Enum

type Status string

const (
    Pending  Status = "pending"
    Approved Status = "approved"
    Rejected Status = "rejected"
)

The Status type has three possible values: "pending", "approved", and "rejected".

Step 2: Define Model

type User struct {
    ID        uint   `gorm:"primary_key"`
    Name      string
    Status    Status
    CreatedAt time.Time
    UpdatedAt time.Time
}

The User model includes a field of the enum type Status.

Step 3: Use Enum in GORM Operations

user := User{Name: "John", Status: Pending}
db.Create(&user)

var users []User
db.Where("status = ?", Approved).Find(&users)

db.Model(&user).Update("status", Rejected)

db.Where("status = ?", Pending).Delete(User{})

Enum values are used in create, query, update, and delete operations.

Alternative Methods

Method 1: Use String Type Directly

type User struct {
    ID   uint
    Role string
}

Using a plain string field can represent roles such as "admin", "moderator", or "user", but it lacks compile‑time checks.

Method 2: Custom Type

type Role string

const (
    Admin     Role = "admin"
    Moderator Role = "moderator"
    User      Role = "user"
)

type User struct {
    ID   uint
    Role Role
}

Defining a custom type with constant values provides compile‑time safety and restricts values to the defined set.

Method 3: GORM Enum Tag

type Role string

const (
    Admin     Role = "admin"
    Moderator Role = "moderator"
    User      Role = "user"
)

type User struct {
    ID   uint
    Role Role `gorm:"type:enum('admin','moderator','user')"`
}

Combining a custom type with GORM's enum column tag creates an actual ENUM column in the database while keeping type safety in Go.

Conclusion

Adding enums to GORM models improves type safety and makes database operations more reliable.