Defining a string in Ruby is pretty simple:

s1 = 'Hello!'
s2 = "This is a string.\n Calculations: 2+2=#{2+2}"

You can use both single and double quotes, however double quotes give you much more – expressions enclosed in #{} would be processed by Ruby before string is shown. Pretty cool, heh?
But I am sure most of you have already known that. Let’s proceed than: consider you have a string, that contains many mixed quotes (‚) and double quotes („). How to write it, if the same marks (‚) and („) are considered as string delimiters? Of course you can concatenate string step by step delimiting single quote with double quoted and vice versa, but this is painful. There is a better solution:

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The simplest mistake sometimes costs several hours of debugging. One of these is checking if the target exists before trying to apply some changes to/using it.

How to check if element in DOM exists, i.e. if the selector $(‚.some_class’) is not empty?

The simplest:

if ($('.some_class')) {
   //some action
}

will not work!

The correct condition uses the .lenght function:

if ($('.some_class').length > 0) {
   //some action
}

Note no brackets after .length.

How to check if JavaScript object’s property exists?

This is tricky, as there are two types of properties: own properties and prototype properties. Not going into details, we can assume, that own properties are the one that are for example serialized by JSON, and prototype properties are the one that can be empty or not, but are given in the object’s definition.

So, in most cases you want to check if the own property exists for the given object. This can be obtained using the hasOwnProperty() method:

if (the_object.hasOwnProperty("name)) {
   //some action
}

If you only want to check whether there is the prototype property, you may use in operator to determine the existence of the property:

if ("name" in the_object)) {
   //some action
}

jqGrid is a powerful jQuery based, AJAX tool for representing and editing tabular data in many formats (database output in JSON, XML etc.).

It is really easy to implement, quite well documented and really easy to style (through jQuery UI themes and its excellent themeroller).

I was working on a Joomla-PHP-MySQL project. I have successfully enabled the extended show functionality, adding edit option also went smoothly. However, I got a little bit stuck while trying to enable Search. Basing on demo examples and some blogs, I have managed to develop a piece of code that successfully made the search work like a charm. Below you’d find a php file responsible for returning the get xml data request from jqgrid.

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I was working on project, that part was a basic tree-like structure of static pages, that needed kind of CMS for client. I had two solutions:

1. implement awesome_nested_set + rails-ckeditor + paperclip
2. find a ready-to-go solution

After a little bit of googling tens of out-of-date pages&blogs, I ended up on a great website http://www.whichrubycmsshouldiuse.com/ by Youssef Chaker.
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In Rails <=2.3 i18n internationalization does not include translation of form labels. However, this can be easily fixed by installing the patch i18n_label by iain. For your Rails project, just install plugin:

ruby script/plugin install git://github.com/iain/i18n_label.git

Now you should just add appropriate entries to your locale file. I’d explain it in the example below.
I have the following form to the model Post:

<% form_for :post do |f| -%>
  <%= f.error_messages %>

  <p><%= f.label :name %></p>
  <p><%= f.text_field :name %></p>

  <p><%= f.submit "Wyślij" %></p>
<% end -%>

I want the label :name to be automatically translated according to the entry in locales. Taking as an example polish locale pl.yml, we have to create new entry:

pl:
  activerecord:
    models:
      post: "Wiadomości"
    attributes:
      post:
        name: "Nazwa"

…and that’s all! After restarting the project, the form labels are successfully tanslated according to locale entries!

It’s time to graduate…

Let’s inference what one learned about doing research and interpreting news during years of studying. Some remarks on science, pseudoscience and how to not fool yourself from Richard P. Feynman in an annual graduation lecture for Caltech students in 1974.

Enjoy the reading!

Cargo Cult Science

(source: http://calteches.library.caltech.edu/51/2/CargoCult.pdf)

I had a task: convert all files (hundreds) in directory from bitmap .bmp to jpg format. You can achive is with one command using ImagesMagic:

mogrify -format jpg *.bmp

See also full manual about mogirfy.

Working on current projects, I found it necessary to create tens of date form fields. The View part is the weekest among MVC in Rails in comparition to other frameworks (Grails…), so it is quite obvious I looked for some helper. The best I have found is Formtastic. I have found a very DRY soultion to add new filed type to formtastic, that would automatically integrate this filed with jQuery UI datepicker.

Step-by-step manual

1. Download jQuery and jQuery UI and include them to your layout with javascript_include_tag and stylesheet_link_tag.

2. I assume you have formtastic gem installed. Then go to Configuration/Initializers/formtastic.rb and add the following lines in the beginning of the file:

module Formtastic
  module DatePicker
    protected

    def datepicker_input(method, options = {})
      format = options[:format] || ActiveSupport::CoreExtensions::Date::Conversions::DATE_FORMATS[:default] || '%d %b %Y'
      string_input(method, datepicker_options(format, object.send(method)).merge(options))
    end

    # Generate html input options for the datepicker_input
    #
    def datepicker_options(format, value = nil)
      datepicker_options = {:value => value.try(:strftime, format), :input_html => {:class => 'ui-datepicker'}}
    end
  end
end
Formtastic::SemanticFormBuilder.send(:include, Formtastic::DatePicker)

3. Add the following lines to public/javascript/application.js:

$(document).ready(function(){
  $('input.ui-datepicker').datepicker();
});

4. Ready! Now you can use a new tag :as => :datepicker inside formtastic tag, as in the following example:

<% semantic_form_for @master do |f| -%>
  <% f.inputs do -%>
    <%= f.input :name %>
    <%= f.input :born, :as => :datepicker %>
  <% end -%>
  <%= f.buttons %>
<% end -%>

I hope it will help Drop a comment if you have any questions.

Update

Thanks to demersus, there is a plugin integrating jQuery UI datepicker with Ruby on Rails Formtastic — thanks!

While looking for a tool that’d help me to generate the database schema diagram, I’ve found RailRoad Ruby gem. However, it was not working with my Rails 2.3.5 + Ruby 1.8.7 on Windows. While running railroad in command line, I was getting an error:

 c:/Ruby/lib/ruby/gems/1.8/gems/railroad-0.5.5/lib/railroad/app_diagram.rb:54:in 'reopen': No such file or directory - /dev/null (Errno::ENOENT)

(...)

This seemed to me as an error similar to RoR: plugin install from GIT repository in Windows error. And luckily it was!

Solution

The soultion is as follows:

1. Go to %ruby_installation_directory\lib\ruby\gems\1.8\gems\railroad-0.5.5\lib\railroad\ and open app_diagram.rb in a text editor.
   (%ruby_installation_directory is c:\Rails by default)
2. Around line 54 find:

   STDOUT.reopen(PLATFORM =~ /mswin/ ? "NUL" : "/dev/null")

   and change it to:

   #STDOUT.reopen(PLATFORM =~ /mswin/ ? "NUL" : "/dev/null")
   	STDOUT.reopen('NUL:')

3. Open controllers_diagram.rb in the same directory with a text editor.
4. Around line 39 find:

   require "app/controllers/application.rb" 

   and change it to:

   require "app/controllers/application_controller.rb" 

5. That’s all! Now you can create for example your Rails project models schema (having Graphvis installed) just typing in command line:

   railroad -a -i -M | dot -Tpng > models.png

Create tasks

To automate the process of creating schemes, you can create Rails task. In your rails_project_dir/Libs/tasks create diagrams.rake and copy the text:

namespace :doc do
  namespace :diagram do
    task :models do
      sh "railroad -a -i -M | dot -Tpng > doc/models.png"
      sh "railroad -i -l -a -m -M | dot -Tsvg doc/models.svg"
    end

    task :controllers do
      sh "railroad -i -l -C | neato -Tsvg > doc/controllers.svg"
    end
  end

  task :diagrams => %w(diagram:models diagram:controllers)

end

Now you can run the task by typing in console: rake doc:diagrams to generate all diagrams (for models an controllers) or rake doc:diagram:models to generate diagram for models only.

Due to the information on RailsRoad Docs, there is a bug in Graphvis while crating svg graphic. There is a simple way to correct it (citation from RailsRoad Docs):

Important: There is a bug in Graphviz tools when generatingSVG files that cause a text overflow. You can solve this problem editing (with a text editor, not a graphical SVG editor) the file and replacing around line 12 „font-size:14.00;” by „font-size:11.00;„, or by issuing the following command (see „man sed„):

sed -i 's/font-size:14.00/font-size:11.00/g' file.svg

Note: For viewing and editing SVG there is an excellent opensource tool called Inkscape (similar to Adobe Illustrator.) For DOTprocessing you can also use Omnigraffle (on Mac OS X).

Since Ruby 1.8.7 and Rails 2.3.5 under MS Windows system there is a common error when you run:

%rails_project_directory> ruby script/plugin install git://github.com/user/project.git

The problem is that no matter what variations and workarounds through comman line would you try:

%rails_project_directory>ruby script\plugin install http://github.com/user/project.git/

you always get the error:

Plugin not found: [git://github.com/user/project.git]

Certainly you could just download a from GIT project and copy/clone it to the vendor/plugins directory of your project. However you must admit it is a pain. Each time I installed manually  a git-hosted plugin (so almost in 95% of Rails plugins :-P), I spent about half an hour looking for a solutions. And this morning I’ve eventually found it on www.ruby-forum.com.

Soultion

The soultion is as follows:

1. Install msysgit if you haven’t done it yet.
2. Go to %ruby_installation_directory\lib\ruby\gems\1.8\gems\activesupport-2.3.5\lib\active_support\core_ext\kernel and open reporting.rb in a text editor.
   (%ruby_installation_directory is c:\Rails by default)
3. Around line 38 find:

   stream.reopen(RUBY_PLATFORM =~ /mswin/ ? 'NUL:' : '/dev/null')

   and change it to:

   #stream.reopen(RUBY_PLATFORM =~ /mswin/ ? 'NUL:' : '/dev/null')
   stream.reopen('NUL:')

4. Save the file and live in a joy and happiness of working git hosted Rails plugin installation