Gin Gonic array of values from PostForm

Question

I'm trying to capture an array of Post values from HTML form using Go / Gin Gonic -- in PHP I would use something like:

<form method="POST" enctype="multipart/form-data" action="mygo">
 <input type=hidden name="emails[]" value="[email protected]">
 <input type=hidden name="emails[]" value="[email protected]">
 <input type=hidden name="emails[]" value="[email protected]">
</form>

However this doesn't seem to work with Gin Gonic (or Go for that matter).

I've also tried:

<form method="POST" enctype="multipart/form-data" action="mygo">
 <input type=hidden name="emails" value="[email protected]">
 <input type=hidden name="emails" value="[email protected]">
 <input type=hidden name="emails" value="[email protected]">
</form>

As elsewhere it is suggested that doing this would cause c.PostForm("emails") to return a slice. However in practice it seems that this instead returns the last value as a string instead :(

Interestingly, c.Request.PostForm returns an empty map, even if c.Request.ParseForm() is called first. What am I doing wrong?

Go Form:

func main() {
// ...
    router.POST("mygo",parseFunc)
}

func mygo(c *gin.Context) {
  c.Request.ParseForm()
  log.Printf("%v",c.Request.PostForm["emails"]) // ""
  log.Printf("%v",c.PostForm("emails") // "[email protected]"
}

Answer 1

In order to make it works you have two ways here

<form method="POST" enctype="multipart/form-data" action="mygo">
 <input type=hidden name="emails" value="[email protected]">
 <input type=hidden name="emails" value="[email protected]">
 <input type=hidden name="emails" value="[email protected]">
</form>

r.POST("/", func(c *gin.Context) {
        c.Request.ParseMultipartForm(1000)
        for key, value := range c.Request.PostForm {
            fmt.Println(key,value)
        }
    })

either

    <form method="POST" action="mygo">
     <input type=hidden name="emails" value="[email protected]">
     <input type=hidden name="emails" value="[email protected]">
     <input type=hidden name="emails" value="[email protected]">
    </form>

 r.POST("/", func(c *gin.Context) {
            c.Request.ParseForm()
            for key, value := range c.Request.PostForm {
                fmt.Println(key,value)
            }
        })

Both gives the same result

emails [[email protected] [email protected] [email protected]]

Answer 2

With the latest version of gin-gonic (v1.2) you can just:

emails := c.PostFormArray("emails")

Then emails will be a []string.

Parse and iterate isn't more necessary.

Answer 3

Issue with this code is two fold. Posting my answer in case someone else has either of these problems.

1. c.Request.PostForm returns empty in this case because the form is multipart and ParseForm only parses non-multipart forms. In order to get the data here either change the form type to non-multipart or call ParseMultipartForm before accessing post values.
2. c.PostForm() only returns the first value because thats what the wrapper in Gin Gonic does. In order to access all the values, it is necessary to access the original c.Request.PostForm data, and then AFTER you parse it properly.

Thanks @JimB for the assist.