Formatting time in golang gorm

preface

Recently, I encountered a problem during the development of a project.

gorm automatically maintains key time fields like created_at, updated_at, and deleted_at. But its principle and drawback need to understand 1.

1. Usage

Control the time format by customizing 1 localtime structure

package utils
import (
 "time"
 //"strconv"
 "fmt"
 "database/sql/driver"
 "strconv"
)
type LocalTime struct {
 time.Time
}
func (t LocalTime) MarshalJSON() ([]byte, error) {
 // Format the seconds 
 seconds := t.Unix()
 return []byte(strconv.FormatInt(seconds, 10)), nil
}
func (t LocalTime) Value() (driver.Value, error) {
 var zeroTime time.Time
 if t.Time.UnixNano() == zeroTime.UnixNano() {
 return nil, nil
 }
 return t.Time, nil
}
func (t *LocalTime) Scan(v interface{}) error {
 value, ok := v.(time.Time)
 if ok {
 *t = LocalTime{Time: value}
 return nil
 }
 return fmt.Errorf("can not convert %v to timestamp", v)
}

The field structure of dao is

type TestDao struct{
   Id    uint    `gorm:"primary_key,AUTO_INCREMENT" json:"id"`
 CreatedAt  LocalTime `json:"-"`
 UpdatedAt  LocalTime `json:"update_at"`
 DeletedAt  *LocalTime `json:"-"`
}

2. Implementation principle

This is actually done by defining the current time through the callback function when save changes. Refer to portal for this article

This allows you to control the time format through the custom LocalTime.

3. Disadvantages and Suggestions

Because fields like createAt are still of type LocalTime when the program runs, it's not easy to copy them yourself.

For example, you want to change the createAt time of the application by 1 while it is running. You can't do it! Because it's of type LocalTime, and your time is either timestamp or 1 string, the type doesn't match... Isn't it embarrassing??

Therefore, it is recommended that such reserved fields should not be modified while the program is running. Just use it as a record or identifier. If you really need to change the time, maintain the contents of the fields yourself. For example, use int to store timestamps or string to store strings. And then every time you change it, you change its value.

You can also wrap the work itself into an callback function so that you can control the field at will. Refer to portal above.

So, just to make fun of it, gorm's implementation of time formatting is so inhumane!

conclusion