Accessing array post params in golang (gin)

Question

I'm attempting to access an array of files and values posted to an API written in Gin (golang). I've got a function which takes a file, height and width. It then calls functions to resize the file, and then upload it to S3. However, I'm attempting to also upload multiple files.

func (rc *ResizeController) Resize(c *gin.Context) {

    file, header, err := c.Request.FormFile("file")
    filename := header.Filename

    if err != nil {
        log.Fatal(err)
    }

    height := c.PostForm("height")
    width := c.PostForm("width")

    finalFile := rc.Crop(height, width, file)

    go rc.Upload(filename, finalFile, "image/jpeg", s3.BucketOwnerFull)

    c.JSON(200, gin.H{"filename": filename})
}

I couldn't see anywhere in the docs how to access data in the following format:

item[0]file
item[0]width
item[0]height
item[1]file
item[1]width
item[1]height

etc.

I figured something along the lines of:

for index, element := range c.Request.PostForm("item") {
    fmt.Println(element.Height)
}

But that threw "c.Request.Values undefined (type *http.Request has no field or method Values)"

jmaloney · Accepted Answer · 2015-10-16 16:21:51Z

3

You can access the File slice directly instead of using the FormFile method on Request. Assuming you have a form array for width and height that correspond to the order that the files were uploaded.

if err := ctx.Request.ParseMultipartForm(32 << 20); err != nil {
    // handle error
}

for i, fh := range ctx.Request.MultipartForm.File["item"] {
    // access file header using fh
    w := ctx.Request.MultipartForm.Value["width"][i]
    h := ctx.Request.MultipartForm.Value["height"][i]
}

The FormFile method on Request is just a wrapper around MultipartForm.File that returns the first file at that key.

edited Oct 16, 2015 at 16:21

answered Oct 16, 2015 at 15:57

jmaloney

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7 Comments

Ewan Valentine Over a year ago

Thanks for your response. Trouble is, I'm trying to get a set of data for each array item if that makes sense. So I'm not just iterating over a series of files, each iteration will contain a height and width value also.

jmaloney Over a year ago

Are you trying to derive the height and width from the uploaded file, or is it inputed when the file is uploaded?

jmaloney Over a year ago

If you are trying to derive the width and height you will have to open the file and decode the image based on mimetype to determine the width and height.

Ewan Valentine Over a year ago

It's just a generic upload, I'm uploading several files, each given a height and width and I have a function which crops that image to the height and width etc. I'm just struggling to access the post data in rows if that makes sense?

jmaloney Over a year ago

Ok. You can just use a regular form array for width and height that correspond to the order that the files were uploaded. Then when you iterate your files you can accesses the form's Value map to get the width and height by index.

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