Detecting font width

http://stackoverflow.com/questions/378887/how-do-i-calculate-a-strings-width-in-ruby

Setting up server hardware time

:~$ sudo date 093019512009
############# ddmmHHMMYYYY

:~$ sudo hwclock --systohc
:~$ sudo hwclock --show

Setting up server hardware time

:~$ sudo date 093019512009
:~$ sudo hwclock --systohc
:~$ sudo hwclock --show

Fixing IE6 & Rails & cookies issue

Problem: Cookies are not set in IE6, as well as session, which depends on cookies.

Problem description: This is caused by default IE6 security option "Block 3rd sites party cookies".

To solve the issue, you need to create Privacy Policy for your site

Here are the steps you need to do in your rails application:

1. Generate privacy policy http://www.alphaworks.ibm.com/tech/p3peditor
2. Put two files p3p.xml and policy.html into /public/w3c/
3. Add

to your apps/views/layout/application.rb
4. Add a header in application_controller.rb in before_filter the following code:
header['P3P'] = 'CP="CAO CURa ..."'

And that's it. Don't forget to clear cookies and restart your IE6.

Useful links:

http://www.oreillynet.com/pub/a/javascript/2002/10/04/p3p.html

Refactoring ruby code #2: Extracting logic to helpers

In this post I want to demonstrate an simple refactoring technique extract method.

Here is an long controller method:



It's obvious that this is not the right place for such logic. So what we do is:
1) Write some tests
2) Create EventsHelper
3) Move all logic from controller to EventsHelper
4) Rewrite test :)

Here is a result:



So, now in views we use previous_moth(@month) instead of @previous_month

What we got:
* Thiner controller
* Separate logic
* Easy testing
* Less variables

Ruby: Refactoring code #1

In these series I'll write some posts on refactoring ruby code.

No matter what language you write, there are always quite similar approach to refactoring.

Refactoring means changing code, improving it's readability and scalability, without functional modification.

Here are some basic steps:
0. Find the code that smells.

1. Check if code has enough test coverage. Write tests if no coverage.
2. Refactor code. Do it by small pieces. Don't try to refactor everything at once. Make this process iterative.
3. Run tests.
4. Refactor tests.
5. Commit changes.


It's really important to refactor code step by step, don't try to refactor big pieces of code. Otherwise you'll lose the clue.

The other important thing is not to change functionality. Even if you see the code has a bug, fix it right after you are done with refactoring.

Testing is very important during whole process of refactoring, you can't be sure for your code without tests.


So, lets jump right to the examples.

First, we need to find stinky code. Most of that you can find in your controllers.

Here is the first candidate for refactoring, we have a CategoriesController, with show method:

  def show
    @category = Category.find(params[:category_id], :include=>[:category_stats])
    @region = Region.find_by_id(params[:region_id]) unless params[:region_id].blank?
    @action = Action.find_by_id(params[:action_id]) unless params[:action_id].blank?

    @alternatives = @category.alternative_categories.counter_caches.to_a

    CategoryStat.category_opened(@category, request.remote_ip)
    key = {:category_id=>@category.id}
    key.merge!(:region_id=>@region.id) if @region
    set_scope_id(key)

    unless show_subcategories?(@category, @region)
      common_args = {:page => params[:page], :per_page => ADS_PER_PAGE,
        :include => [:custom_attributes, :price_unit, :category, :assets, :region],
        :order => order, :conditions=>filter_conditions}

      ad_scope = AdList.category_or_children(@category)
      ad_scope = ad_scope.active
      ad_scope = ad_scope.action(@action.id) if @action
      ad_scope = ad_scope.region(@region) if @region
      ad_scope = ad_scope.created_after(DateFilter.value(date_filter)) if date_filter_applied?

      if region_selected?
        @regional_ads = ad_scope.region(current_region).paginate(common_args)
        ad_scope = ad_scope.not_in_ids(@regional_ads.collect{|a| a.id}) unless @regional_ads.empty?
      end

      @ads = ad_scope.paginate(common_args)
    end
  end

As we can see, the method is really big, and this is kind of problem. So the first step would be getting rid of show_subcategories? conditions by spliting it to two different methods.

So we have the following:

def messages
    @category = Category.find(params[:category_id], :include=>[:category_stats])
    @region = Region.find_by_id(params[:region_id]) unless params[:region_id].blank?
    @action = Action.find_by_id(params[:action_id]) unless params[:action_id].blank?

    @alternatives = @category.alternative_categories.counter_caches.to_a

    CategoryStat.category_opened(@category, request.remote_ip)
    key = {:category_id=>@category.id}
    key.merge!(:region_id=>@region.id) if @region
    set_scope_id(key)
    
    common_args = {:page => params[:page], :per_page => ADS_PER_PAGE,
        :include => [:custom_attributes, :price_unit, :category, :assets, :region],
        :order => order, :conditions=>filter_conditions}

      ad_scope = AdList.category_or_children(@category)
      ad_scope = ad_scope.active
      ad_scope = ad_scope.action(@action.id) if @action
      ad_scope = ad_scope.region(@region) if @region
      ad_scope = ad_scope.created_after(DateFilter.value(date_filter)) if date_filter_applied?

      if region_selected?
        @regional_ads = ad_scope.region(current_region).paginate(common_args)
        ad_scope = ad_scope.not_in_ids(@regional_ads.collect{|a| a.id}) unless @regional_ads.empty?
      end

      @ads = ad_scope.paginate(common_args)
  end

  def show
    @category = Category.find(params[:category_id], :include=>[:category_stats])
    @region = Region.find_by_id(params[:region_id]) unless params[:region_id].blank?
    @action = Action.find_by_id(params[:action_id]) unless params[:action_id].blank?

    @alternatives = @category.alternative_categories.counter_caches.to_a

    CategoryStat.category_opened(@category, request.remote_ip)
    key = {:category_id=>@category.id}
    key.merge!(:region_id=>@region.id) if @region
    set_scope_id(key)
  end

So now we have a small duplication, here is how we can handle this:

before_filter :find_category_region_action, :only => [:show, :messages]
  
  def find_category_region_action
    @category = Category.find(params[:category_id], :include=>[:category_stats])
    @region = Region.find_by_id(params[:region_id]) unless params[:region_id].blank?
    @action = Action.find_by_id(params[:action_id]) unless params[:action_id].blank?

    @alternatives = @category.alternative_categories.counter_caches.to_a

    CategoryStat.category_opened(@category, request.remote_ip)
    key = {:category_id=>@category.id}
    key.merge!(:region_id=>@region.id) if @region
    set_scope_id(key)
  end

So now we have two clean methods with no duplication.

Wrap long text with ruby

Here is a code snipet on how to wrap long texts.

It actually do long lines ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa') and ('adas asdas asdas dad asdasd ad') wrapping with ' ' and




Thanks to http://blog.macromates.com/2006/wrapping-text-with-regular-expressions/

Data migrations with rails

data_migration plugin

Sinatra. First aplication

Recently tried a sinatra framework for a small web app.

Sinatra is actually cool thing. It's easy to start and configure. But I still not sure if it fits for larger than small applications.

I've coded a small app with almost the same structure as a rails application. It could be useful to get started.

Testing Rails plugins

Here's a short list on how to test your plugins.

1) Structure

vendor/
  plugins/
    yourplugin/
      test/
        helper.rb
        your_test.rb
        database.yml
        schema.rb
      init.rb
      Rakefile

2) Rakefile


3) helper.rb


4) your_test.rb


5) schema.rb


6) Running tests
Go to your plugin root folder and run
$ rake test

To see full example, refer to http://github.com/balepc/ip_geolocation/

Here are some other useful links:

Rails plugin testing guide
Another guide