Ignore createdAt field when creating/updating but return JSON response

When performing data creation or update operations, sometimes we want to ignore the value of the createdAt field and just keep its default value. The purpose of this is to use the same timestamp every time the data is created or updated, without causing data inconsistency due to manually setting the timestamp. At the same time, we also want to retain the default value of the createdAt field when returning the JSON response. In PHP, we can achieve this function through some simple operations, thereby improving the readability and maintainability of the code. This article will introduce how to ignore the createdAt field when creating/updating in PHP, but retain its default value when returning a JSON response.

Question content

I have a structure in Go

type ExternalSystem struct {
    ID        uint            `gorm:"primary_key"`
    Name      string          `json:"name" binding:"required"`
    CreatedAt *time.Time      `json:"createdAt" binding:"-"`
    DeletedAt *gorm.DeletedAt `json:"deletedAt" binding:"-"`
}

And has a controller (route)

func CreateExternalSystemAction(c *gin.Context) {
    appG := app.Gin{C: c}

    externalSystem := models.ExternalSystem{}

    if err := c.ShouldBindJSON(&externalSystem); err != nil {
        appG.C.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
            "error": err.Error(),
        })
        return
    }

    db := models2.DB
    db.Create(&externalSystem)

    appG.C.JSON(http.StatusCreated, externalSystem)
}

func UpdateExternalSystemAction(c *gin.Context) {
    appG := app.Gin{C: c}
    db := models2.DB

    var externalSystem models.ExternalSystem

    db.Where("id = @id", sql.Named("id", c.Param("id"))).First(&externalSystem)

    if err := c.ShouldBindJSON(&externalSystem); err != nil {
        appG.C.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
            "error": err.Error(),
        })
        return
    }

    db.Updates(&externalSystem)

    appG.C.JSON(http.StatusOK, externalSystem)
}

How to ignore the completion of fields CreatedAt/UpdatedAt when creating or updating an object? This way the server (not the client) is responsible for filling in the fields, so what will the JSON send me? However, I need the value of this field to be sent to the client in the response.

Currently when I send JSON:

{
    "name": "System 3",
    "createdAt": "2023-12-25T22:04:10.012034+04:00"
}

Gin binds this value to the structure. To summarize again, I want to ignore these write fields (when received from the client) but give them in the read response.

I have tried before:

Binding: "-" but this doesn't work (bid verification)

json: "-" but this hides the response field

Solution

I have been thinking about the solution for a long time. After reading the comments under my question. I made a choice that worked perfectly for me. However, the approach is still not similar to what I've used in other languages ​​(PHP Symfony, Python Django)

model

type System struct {
    ID        uint
    Name      string
    CreatedAt time.Time
    UpdatedAt time.Time
}

type InputSystem struct {
    Name string
}

func (inputSystem *InputSystem) Convert() System {
    system := System{
        Name: inputSystem.Name,
    }
    return system
}

func (system *System) Save() (*System, error) {
    err := DB.Create(system).Error

    if err != nil {
        return &System{}, err
    }

    return system, err
}

func (system *System) BeforeSave(*gorm.DB) error {
    system.Name = html.EscapeString(strings.TrimSpace(system.Name))
    return nil
}

func (system *System) BeforeUpdate(*gorm.DB) error {
    system.Name = html.EscapeString(strings.TrimSpace(system.Name))
    return nil
}

Controller(route)

func CreateSystemAction(c *gin.Context) {

    var inputSystem models.InputSystem

    if err := c.BindJSON(&inputSystem); err != nil {
        c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
            "error": err.Error(),
        })
        return
    }

    dbSystem := inputSystem.Convert()

    _, err := dbSystem.Save()
    if err != nil {
        return
    }

    c.JSON(http.StatusCreated, dbSystem)
}

If there are better suggestions, I will be happy to receive comments

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