Ankit working with Rails interesting thoughts for ruby and rails development

While using guard with Rails 4, I have faced an error:

FATAL: Listen error: unable to monitor directories for changes.

 WARNING: Can't verify CSRF token authenticity

This warning appears while I'm trying to do jQuery ajax request.

I have faced this issue while upgrading my older rails app to rails 3.2.

This issue solved by adding bellow lines in head section in layout of application for me.

    <%= csrf_meta_tag %>

    <%= javascript_tag do %>
      jQuery(document).ajaxSend(function(e, xhr, options) {
       var token = jQuery("meta[name='csrf-token']").attr("content");
        xhr.setRequestHeader("X-CSRF-Token", token);
      });
    <% end %>

The session was being reset in each ajax request (GET, POST, PUT, DELETE).
Adding the above mentioned code resolved my issue.

In ruby, we can find time from/to epoch time as below:


To find current epoch time in seconds (10 digit) use below code,
    current_epoch_time =( Time.now.to_i)
                          or
    current_epoch_time =( Time.now.to_f).ceil

To find current epoch time in mili-seconds (13 digit) use below code,
    current_epoch_time =( Time.now.to_f*1000).ceil

If we want Time from epoch time then use below code,

begin
   Time.at(current_epoch_time)
rescue RangeError => e
   Time.at(current_epoch_time / 1000)
end

In above code,
1. current_epochtime is in integer.
2. If epochtime is in miliseconds (13 digit) then it will raise RangeError.
3. We have catch RangeError and find datetime accordingly.


I hope it's useful to work with epoch time in ruby.

You can find images from given web-url by using following code:

For this first you need to write below statements in your .rb file.

require "open-uri"
require "nokogiri"
require "image_size"


now use below code:

  def fetch_images(url)
    return [] if url.nil?
    url_content = open(url)
    url_data = Nokogiri::HTML(url_content)
    images = []
    url_data.xpath("/html/body//img").each do |img|
       src = img["src"]
       full_img_src = src.match(/^(http|https):\/\//) ? src : File.join(url,src)
       if valid_image(full_img_src)
        images << full_img_src
       end
    end
    return images
  rescue
     return 0
  end

  def valid_image(img_url)    return false if img_url.nil?
    valid_img = false
    img_data = open(img_url, "rb").read
    min_size  = [100,100]
    img_size = ImageSize.new(img_data).size
    if img_size[0] >= min_size[0] and img_size[1] >= min_size[1]
      valid_img = true
    end
    return valid_img
  rescue
    return false
  end

Here I have restricted images to fetch only (100x100) sized images.

One of my colleague has done multiple db connection in rails


Here is his work,




From, http://blog.brijeshshah.com/multiple-database-connections-in-rails/


it's really helpful.