如何在ShouldBindJSON()中使用结构的一部分？

huangapple
go评论179阅读模式
英文:

How to use a part of struct in ShouldBindJSON()?

问题

我正在使用Go 1.17和Gin。这是我的结构体：

  1. package model
  3. type Movie struct {
  4.     ID         string `json:"id"`
  5.     Year       uint16 `json:"year" binding:"required,lt=3000"`
  6.     RentNumber uint32 `json:"rent_number" db:"rent_number" binding:"required,lt=4294967290"`
  7.     Title      string `json:"title" binding:"required,max=255"`
  8.     Author     string `json:"author" binding:"required,max=80"`
  9.     Editor     string `json:"editor" binding:"required,max=125"`
  10.     Index      string `json:"index" binding:"required,max=125"`
  11.     Bib        string `json:"bib" binding:"required,max=20"`
  12.     Ref        string `json:"ref" binding:"required,max=20"`
  13.     Cat1       string `json:"cat_1" db:"cat_1" binding:"required,max=20"`
  14.     Cat2       string `json:"cat_2" db:"cat_2" binding:"required,max=10"`
  15. }

我在某个处理程序中使用这个结构体时遇到了问题。在这个处理程序中，我只需要使用电影结构体的两个属性（Title和Year）。如果我像这样做：

  1. func (h *Handler) myHandler(c *gin.Context) {
  2.     var movie model.Movie
  4.     if err := c.ShouldBindJSON(&movie); err != nil {
  5.         c.Error(err)
  6.         c.Abort()
  7.         return
  8.     }
  9.     ...
  10. }

这样是行不通的，因为在这个Web服务中，我只会发送2个属性，并且我会从绑定标签中得到所需的错误：

  1. {
  2.     "title": "My title",
  3.     "year": 2017
  4. }

所以我想知道处理这个问题的"Go方式"是什么？我可以看到3种解决方案。

  • 使用电影结构体，忽略除了Title和Year之外的所有字段，但是我该如何做到这一点？
  • 创建一个只包含所需字段的特定结构体。在这种情况下，我不会将这个结构体放在model包中，而是放在我的电影API包中。
  1. type StructForTheSpecialHandler struct {
  2.     Year  uint16 `json:"year" binding:"required,lt=3000"`
  3.     Title string `json:"title" binding:"required,max=255"`
  4. }
  • 在我的处理程序中直接创建结构体，像这样：
  1. func (h *Handler) myHandler(c *gin.Context) {
  2.     var tmp struct {
  3.         Year  uint16 `json:"year" binding:"required,lt=3000"`
  4.         Title string `json:"title" binding:"required,max=255"`
  5.     }
  7.     if err := c.ShouldBindJSON(&tmp); err != nil {
  8.         c.Error(err)
  9.         c.Abort()
  10.         return
  11.     }
  12.     ...
  13. }

你能告诉我是否有更好的解决方案，或者告诉我在我的3个解决方案中哪个是正确的方式？

英文:

I'm using Go 1.17 with Gin. Here is my struct:

  1. package model
  3. type Movie struct {
  4. 	ID         string `json:"id"`
  5. 	Year       uint16 `json:"year" binding:"required,lt=3000"`
  6. 	RentNumber uint32 `json:"rent_number" db:"rent_number" binding:"required,lt=4294967290"`
  7. 	Title      string `json:"title" binding:"required,max=255"`
  8. 	Author     string `json:"author" binding:"required,max=80"`
  9. 	Editor     string `json:"editor" binding:"required,max=125"`
  10. 	Index      string `json:"index" binding:"required,max=125"`
  11. 	Bib        string `json:"bib" binding:"required,max=20"`
  12. 	Ref        string `json:"ref" binding:"required,max=20"`
  13. 	Cat1       string `json:"cat_1" db:"cat_1" binding:"required,max=20"`
  14. 	Cat2       string `json:"cat_2" db:"cat_2" binding:"required,max=10"`
  15. }

I have a problem to use this struct in a certain handler. In this handler I just need to use 2 properties (Title and Year) from my movie struct. If I'm doing something like this:

  1. func (h *Handler) myHandler(c *gin.Context) {
  2. 	var movie model.Movie
  4. 	if err := c.ShouldBindJSON(&movie); err != nil {
  5. 		c.Error(err)
  6. 		c.Abort()
  7. 		return
  8. 	}
  9.     ...

It will not working because on this web service I'll send only 2 properties and I'll get the required errors from the binding tags:

  1. {
  2.     "title": My title",
  3.     "year": 2017
  4. }

So I want to know what is the "go way" to handle this ? I can see 3 solutions.

  • Use the movie struct and ignoring all fields except Title andYear, but how I can do that ?

  • Create a specific struct with just the needed fields. In this case I'll not place this struct in the model package but in my movie api package

    1.  type StructForTheSpecialHandler struct {
    2.     Year       uint16 `json:"year" binding:"required,lt=3000"`
    3.     Title      string `json:"title" binding:"required,max=255"`
    4.  }

  • Create the struct directly in my handler like this:

    1. func (h *Handler) myHandler(c *gin.Context) {
    2.    var tmp struct {
    3.  	  Year  uint16 `json:"year" binding:"required,lt=3000"`
    4.  	  Title string `json:"title" binding:"required,max=255"`
    5.    }
    7.    if err := c.ShouldBindJSON(&tmp); err != nil {
    8.  	  c.Error(err)
    9.  	  c.Abort()
    10.  	  return
    11.    }
    12.    ...

Can you tell me if you have a better solution or tell me what is the right way between my 3 solutions?

答案1

得分: 3

你可以直接解组（unmarshal）它（完全绕过验证）：

  1. err := json.NewDecoder(c.Request.Body).Decode(&movie)

或者你可以尝试将这些属性嵌入到结构体中：

  1. type EmbeddedMovieFields struct {
  2.    Year  uint16 `json:"year" binding:"required,lt=3000"`
  3.    Title string `json:"title" binding:"required,max=255"`
  4. }
  6. type Movie struct {
  7.     EmbeddedMovieFields
  8.     ID         string `json:"id"`
  9.     RentNumber uint32 `json:"rent_number" db:"rent_number" binding:"required,lt=4294967290"`
  10.     Author     string `json:"author" binding:"required,max=80"`
  11.     Editor     string `json:"editor" binding:"required,max=125"`
  12.     Index      string `json:"index" binding:"required,max=125"`
  13.     Bib        string `json:"bib" binding:"required,max=20"`
  14.     Ref        string `json:"ref" binding:"required,max=20"`
  15.     Cat1       string `json:"cat_1" db:"cat_1" binding:"required,max=20"`
  16.     Cat2       string `json:"cat_2" db:"cat_2" binding:"required,max=10"`
  17. }
  19. var movie model.EmbeddedMovieFields
  21. if err := c.ShouldBindJSON(&movie); err != nil {
  22.     c.Error(err)
  23.     c.Abort()
  24.     return
  25. }
英文:

You could just unmarshal it directly (bypassing the validation completely):

  1. err := json.NewDecoder(c.Request.Body).Decode(&movie)

Or you could try to embed those properties in the struct:

  1. type EmbeddedMovieFields struct {
  2.    Year  uint16 `json:"year" binding:"required,lt=3000"`
  3.    Title string `json:"title" binding:"required,max=255"`
  4. }
  6. type Movie struct {
  7.     EmbeddedMovieFields
  8.     ID         string `json:"id"`
  9.     RentNumber uint32 `json:"rent_number" db:"rent_number" binding:"required,lt=4294967290"`
  10.     Author     string `json:"author" binding:"required,max=80"`
  11.     Editor     string `json:"editor" binding:"required,max=125"`
  12.     Index      string `json:"index" binding:"required,max=125"`
  13.     Bib        string `json:"bib" binding:"required,max=20"`
  14.     Ref        string `json:"ref" binding:"required,max=20"`
  15.     Cat1       string `json:"cat_1" db:"cat_1" binding:"required,max=20"`
  16.     Cat2       string `json:"cat_2" db:"cat_2" binding:"required,max=10"`
  17. }
  19. var movie model.EmbeddedMovieFields
  21. if err := c.ShouldBindJSON(&movie); err != nil {
  22.     c.Error(err)
  23.     c.Abort()
  24.     return
  25. }

huangapple
  • 本文由 发表于 2021年11月25日 03:46:31
  • 转载请务必保留本文链接：https://go.coder-hub.com/70102090.html
  • go
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