ruby-on-railsajaxruby-on-rails-3jquerycanvas

How to trigger download with Rails send_data from AJAX post

I'm trying to use send_data to return a PNG image as the response for a ajax post request. How do I get the browser to trigger a download on the success callback?

Details

I'm generating a large base64 image using canvas.toDataURL(), and then posting it to Rails (v3.2.6). Rails decodes it to a binary PNG, and sends the image back to the client.

I've also tried send_file but it has the same issue.

Other options

  1. Download image client side: We can't do this because (1) Safari crashes on large base64 URLs, and (2) Safari does not yet support the download attribute on anchor tags which I would need to specify the downloaded image filename.

  2. Use a $.get instead of $.post: We can't do this because we need to send our canvas.toDataURL() with the request to the server. GET requests URIs have size limitations.

Solution

  • create a function in controller

    def ajax_download
  send_file "path_to_file/" + params[:file]
end

    and then in controller action

    respond_to do |format|
  @java_url = "/home/ajax_download?file=#{file_name}"
  format.js {render :partial => "downloadFile"}
end

    and make a partial in view folder name with _downloadFile.js.erb and write this line

    window.location.href = "<%=@java_url %>"