Bind formdata with array input.

[mytc]

I having having problem with binding the form data.
The input would be like this

<input name="codes[1][icode]" type="number" />
<input name="codes[1][limit]" type="text" />
<input name="codes[2][icode]" type="number" />
<input name="codes[2][limit]" type="text" />

And the struct

type Event struct {
	gorm.Model
	Code []InvideCode `form:"codes"`
}


type InvideCode struct {
	gorm.Model
	EventID uint 
	Code string `form:"icode"`
	Limit string `form:"limit"`
}

And i bind it with
event := new(Event)
or
c.FormValue("codes")

Both give me the empty value.
What did I done wrong?

Actually there is similar problem was asked at SO , the accepted answer is using 3rd party library and I don't like it. I wonder if there any Echo way to do it.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed within a month if no further activity occurs. Thank you for your contributions.

[lammel]

Data binding was improved with Echo v4.2. Please check the docs for request binding
Please close if this is resolved for you @mytc

[kidlj]

The latest several versions of Echo supports this behavior like the following:

type Event struct {
	gorm.Model
	Code []InvideCode `form:"codes[]"`
}

[dovoselly]

The latest several versions of Echo supports this behavior like the following:

type Event struct {
	gorm.Model
	Code []InvideCode `form:"codes[]"`
}

It returned an empty array

[kidlj]

The latest several versions of Echo supports this behavior like the following:

type Event struct {
	gorm.Model
	Code []InvideCode `form:"codes[]"`
}

It returned an empty array

I haven't read the source code of Echo for this part, but it works for my slightly different cases:

<form>
			<div class="items">
				{{range .Names}}
				<input type="checkbox" id="{{.ID}}" name="ids[]" value={{.ID}} hidden>
				<label for="{{.ID}}">{{.Name}}</label>
				{{end}}
			</div>
</form>

With this handler:

type examPayload struct {
	IDs []int `form:"ids[]"`
}

func (h *Handler) createExam(c echo.Context) error {
	payload := new(examPayload)
	err := c.Bind(payload)
	if err != nil {
		return echo.ErrBadRequest
	}

	if len(payload.IDs) == 0 {
		return echo.ErrBadRequest
	}

	u, err := h.userService.GetUserFromContext(c)
	if err != nil {
		return echo.ErrUnauthorized
	}

	exam, err := h.service.CreateExam(c.Request().Context(), u.ID, payload.IDs)
	if err != nil {
		return echo.ErrInternalServerError
	}

	return c.Redirect(http.StatusSeeOther, fmt.Sprintf("/exam?id=%d", exam.ID))
}

I didn't test for op's case, sorry.

[aldas]

Echo supports binding data to slices when form value is named codes[] but not codes[N] where N is "dynamic" in form value name.

When you post

<input name="codes[1][icode]" type="number" />
<input name="codes[1][limit]" type="text" />
<input name="codes[2][icode]" type="number" />
<input name="codes[2][limit]" type="text" />

What Echo sees from Request is 4 different form values with following names:

• codes[1][icode]
• codes[1][limit]
• codes[2][icode]
• codes[2][limit]

There is no (currently) built in magic to guess from brackets and number if it is suppose to be array of things. I am quite sure there are plenty of libraries that can extract form values from Go standard library Request struct like that (Echo is built on Go standard library Request struct)

[Septrum101]

you can use
https://pkg.go.dev/github.com/go-playground/form/v4@v4.2.0#Decoder.Decode
to bind data to struct not map. It seems that there is no magic like laravel to parse formdata.