I am writing PostgreSQL table schema.
type TestTable struct {
ID int `gorm:"column:id;primaryKey;autoIncrement"`
CarType string `gorm:"column:car_type"`
}
So how can i add car types like "SEDAN", "HATCHBACK", "MINIVAN" as enum data type
Assuming you are using GORM with PostgreSQL. First in your database create a type.
CREATE TYPE car_type AS ENUM (
'SEDAN',
'HATCHBACK',
'MINIVAN');
Then you will need to define the following model:
import "database/sql/driver"
type carType string
const (
SEDAN carType = "SEDAN"
HATCHBACK carType = "HATCHBACK"
MINIVAN carType = "MINIVAN"
)
func (ct *carType) Scan(value interface{}) error {
*ct = carType(value.([]byte))
return nil
}
func (ct carType) Value() (driver.Value, error) {
return string(ct), nil
}
type MyTable struct {
gorm.Model
CarType carType `gorm:"type:car_type"`
}
func (MyTable) TableName() string {
return "my_table"
}
Note for MySQL users, you can add struct tag gorm: or sql: so you don't have to run raw query to create enum in the database.
CarType carType `gorm:"type:enum('SEDAN', 'HATCHBACK', 'MINIVAN')";"column:car_type"`
OR
CarType carType `sql:"type:ENUM('SEDAN', 'HATCHBACK', 'MINIVAN')" gorm:"column:car_type"`
enum but we can represent it. Follow the first 3 responses to the following question, it will help you understanding enums in golang . stackoverflow.com/questions/14426366/… On the other part, I think you can try without creating enum in the database. But still without it being enum in the database, you will be risking parsing non-constant values in the database to the constants in your program. I think it's unsafe.
sql:"car_type" is just creating a text(string) column in postgres DB, I already have created the enum in my DB. I tried everything, no error is thrown, don't know whats the problem. Anyone having the same issue or resolution please reply.
gorm:"type:car_type"
Edit: someone pointed out this only works with MySQL. I would take my answer down but someone using MySQL may find it helpful.
Here's an answer that doesn't require you to create a SQL type beforehand. My source for this solution was this github issue
For your field tag, use this:
type TestTable struct {
ID int `gorm:"column:id;primaryKey;autoIncrement"`
CarType carType `sql:"type:ENUM('SEDAN', 'HATCHBACK', 'MINIVAN')" gorm:"column:car_type"`
}
You'll also need to add the Scan and Value methods attached to your carType type.
type carType string
const (
SEDAN carType = "SEDAN"
HATCHBACK carType = "HATCHBACK"
MINIVAN carType = "MINIVAN"
)
func (self *carType) Scan(value interface{}) error {
*self = carType(value.([]byte))
return nil
}
func (self carType) Value() (driver.Value, error) {
return string(self), nil
}
in order to extend Nick's answer I am adding the following for automation:
Assuming you have DBClient struct, you can create a method that creates this car type:
func (psqlClient *DBClient) CreateCarTypeEnum() error {
result := psqlClient.db.Exec("SELECT 1 FROM pg_type WHERE typname = 'car_type';")
switch {
case result.RowsAffected == 0:
if err := psqlClient.db.Exec("CREATE TYPE car_type AS ENUM ('SEDAN', 'HATCHBACK', 'MINIVAN');").Error; err != nil {
log.Error().Err(err).Msg("Error creating car_type ENUM")
return err
}
return nil
case result.Error != nil:
return result.Error
default:
return nil
}
}
on a side note- if you decide to go with slightly different approach:
you can define your enums as int, and leverage iota. then you can use code generator to create sql Scaner/Valuer but also json/text representations.
for example:
https://github.com/dmarkham/enumer
Just like you write in sql, you can use type and add whatever datatype you want like you write in sql.
type MyTable struct {
CarType string `gorm:"column:car_type;type:enum('SEDAN','HATCHBACK','MINIVAN')" json:"car_type"`
}
An update, it will not work with sql:"car_type" instead use gorm:"car_type". That too once you have manually created the custom enum type into the database.
https://gorm.io/docs/data_types.html => impl Scan & Value methods.
If enum is generated by protoc, can use this plugin
https://github.com/yangyang5214/protoc-gen-gorm-serializer .
# task.proto
syntax = "proto3";
enum TaskStatus {
Unknown = 0;
Running = 1;
Exiting = 2;
Pending = 3;
}
# gen gorm-serializer.pb.go
protoc --proto_path=. --go_out=paths=source_relative:. --gorm-serializer_out=paths=source_relative:. task.proto
# use
type Task struct {
gorm.Model
Name string
Status example.TaskStatus `gorm:"type:int"`
}
