Post javascript array to RoR controller using a form hidden field

Question

After browsing many solutions which didn't fit or solve my problem I post this question here:

I use javascript to populate hidden fields in a form with data and send it to a rails controller. This works fine with normal variables but I can't get it to work with arrays. This is what I do:

Javascript (jQuery):

$("#my_form").submit(function() {
    var testvar = 5;
    var testarr = [];
    testarr[0] = "test data";
    testarr[1] = "other data";

    $('input[name=testvar]').val(testvar);
    $('input[name=testarr]').val(JSON.stringify(testarr));
})

RoR controller:

def create
    testvar = params[:testvar]
    data = params[:testarr]
    testarr = ActiveSupport::JSON.decode(data)
    // other commands
end

It works fine for testvar but for the array it always creates the error

can't convert nil into String

What am I doing wrong?

The request looks like this:

{"utf8"=>"✓",
 "authenticity_token"=>"1qFA3NTqUxoI1jusbwrVi5AWIpJz9tbUGR0KuCtNKTs=",
 "testvar"=>"5",
 "testarr"=>"[\"test data\",
 \"other data\"]",
 "commit"=>"Submit my form data"}

Thanks in advance, your help is highly appreciated!

house9 · Accepted Answer · 2012-06-17 17:16:47Z

1

If you name your input fields with [] at the end, rails will map it to params as an array

<input type="hidden" name="testarr[]" />

$(....).val(testarr.join(","))

Or append a new input for each instead of join, they all have the same input name

$(....).submit(....
  $form = $(this)
  testarr.each
    $form.append('<input type="hidden" name="testarr[]" value="...itemValue..." />')

In controller

params[:testarr].each do ....

Typed on an ipad, please forgive incomplete code, hopefully it gives you some ideas

answered Jun 17, 2012 at 17:16

house9

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1 Comment

Chris Over a year ago

I was actually doing this last night and just split on ',' in the controller but obviously this is much better. Awesome!

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