CODEWITHSUNDEEP
ruby-on-railsajax
svelandiag
svelandiag

Reputation: 4320

format.js and format.json in same respond_to

Im a little bit confused about how both can work together format.js and format.json

I have an ajax request and this is the controller action:

def import_contacts_submit
    @new_file = ContactsFile.new(contacts_file_params)
    respond_to do |format|
      @new_file.save
      format.js
      format.json { render json: @new_file.errors, status: :unprocessable_entity } if @new_file.has_errors?
    end
  end

as it is, only the format.js seems to be working, because the error callback I have in the ajax request never runs. But if I move the format.json above the format.js then the error callback in ajax triggers and the format.js never runs.

Upvotes: 1

Views: 865

Answers (2)

stwienert
stwienert

Reputation: 3632

Rails determines the format to take, by reading the Accept header of the http request:

Example:

  def test
      f.js {
        render js: "Hello World"
      }
      f.json {
        render json: { foo: :bar }
      }
    end

curl localhost:3000/test -H 'Accept: application/json'
{"foo":"bar"}%

curl localhost:3000/test -H 'Accept: application/javascript'
Hello World%

Try changing the header accept in your XHR call, e.g. when using fetch:

fetch(url, { 
  headers: { 'Accept': 'application/json' },
})

Similar in jquery's.ajax or raw XHtmlRequest.

Update Rails Content negotiation:

Rails has a heuristic for determine the format. Check the Doc: https://api.rubyonrails.org/classes/ActionDispatch/Http/MimeNegotiation.html#method-i-formats

formats.first will be taken as the "format" for the request, and the order is like this. First rule will "win":

  1. a parameter called "format", e.g. ?format=json
  2. Accept header
  3. path suffix, e.g. /foo/bar.json
  4. When XHR -> Always js
  5. otherwise HTML

Upvotes: 2

Vasfed
Vasfed

Reputation: 18504

In addition to Accept header you can explicitly state format in url:

some_path/to/import_contacts_submit.js
some_path/to/import_contacts_submit.json

Upvotes: 2

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