Question

Is posible send more than one format, something like:

<%= form_for(@post, :format => :json, :csv, :xml) do |f| %>
  ...
<% end %>

Thank you very much!

Answer 1

You don’t “send a format”, you send a request to the server, which responds to this request in the specified format. You can use a parameter to tell the controller which format you want it to return.

There are several ways to tell the controller which format you want. Actually there’s only one way, passing a parameter, but there are several ways to pass this parameter.

I like the hidden_field method, in which you add a hidden field with the value being the format you want, and change the value of this field using javascript when a user selects a radio button with the format, for example. You can also do this using more than 1 submit button, and having the HTML onClick attribute set to a function that changes the value of the hidden_field.

Example (I’ll use the multi-button method, and use jQuery):

First, let’s build the form:

<%= form_for(@post, :format => :json, :csv, :xml) do |f| %>

...

<%= f.hidden_field :random_param_name, :value => "default format value" %>

// Notice you should use f.submit here instead of button_tag, because it's a form_for, not a form_tag

<%= f.submit "Give me XML!", :onClick => "changeFormat('xml');" %>
<%= f.submit "Give me JSON!", :onClick => "changeFormat('json');" %>
<%= f.submit "Give me CSV!", :onClick => "changeFormat('csv');" %>

<% end %>

Now we add the changeFormat function:

<script type="text/javascript">
    function changeFormat(format) {
        // The ID here is in the format "model_name_field_name". This is default for any form_for.
        $("#post_random_param_name").val(format);
    }
</script>

Now you just need to catch this parameter in the controller (params[:post][:random_param_name]) and do what you have to do! One last thing you need to do is adding this random_param_name to the accessible attributes of the Post model:

attr_accessor :random_param_name
attr_accessible :random_param_name