MyFunnyDev » Ruby

rendering generic views in rails 3

Michał Kuklis — Mon, 27 Sep 2010 12:40:16 +0000

# serve mustache templates
class TemplatesController < ActionController::Metal
# include render functionality
include ActionController::Rendering

append_view_path Rails.root.join("app", "views")

def serve
if env["PATH_INFO"] =~ /^\/templates\/(.+)$/
key = $1
begin
render :file => "templates/properties/_#{key}.html.mustache"
rescue
self.status = :file_not_found
self.content_type = 'text/plain'
self.response_body = ''
end
else
self.status = :file_not_found
self.content_type = 'text/plain'
self.response_body = ''
end
end
end

managing gems with rvm named gem sets

Michał Kuklis — Mon, 31 May 2010 03:20:44 +0000

RVM (Ruby Version Manager) is a tool which lets you install and switch between multiple ruby versions. RVM has also something called Named Gem Sets. This is pretty cool because you can create many different gem sets for different types of apps. Here is how to do it (I assume you have rvm already installed if not check this out):

go to your project folder and create new file called .rvmrc
open .rvmrc and add rvm ruby-version@your-gem-set for example rvm ruby-1.9.1@railsgems
close file and type: rvm gemset create your-gem-set (this will create new set)
type gem list (you should see empty list with no gems installed)

It’s almost as you would start with a fresh system.

dfs in ruby :)

Michał Kuklis — Thu, 14 Jan 2010 05:38:42 +0000

I wrote simple dfs in ruby:

def dfs(node, value, queue)
return false if node.nil?
return true if node.data == value

queue.push node.right unless node.right.nil?
queue.push node.left unless node.left.nil?

dfs(queue.pop, value, queue)
end

for node:

class Node
attr_accessor :left, :right, :data
end

class variables, class instance variables and instance variables in ruby

Michał Kuklis — Wed, 13 Jan 2010 06:03:22 +0000

This was covered multiple times already. I’ve created this little snippet to remember the difference between different types of variables in ruby:

class A
@@foo = "class variable of the class A"
@foo = "class instance variable of the class A"

def instance_method
@foo = "instance variable of the class A"
end

def self.class_method1
# class variables are visible to and shared by the instance and class methods
@@foo
end

def self.class_method2
# class instance variables are visible to and shared by the class methods
@foo
end
end

p A.new.instance_method # instance variable of the class A
p A.class_method1 # class variable of the class A
p A.class_method2 # class instance variable of the class A

class B < A
@@foo = "class variable of the class B"
@foo = "class instance variable of the class B"
end

p B.class_method1 # class variable in B
# class variable in A is overwritten by one in B !!!
p A.class_method1 # class variable in B

p B.class_method2 # class instance variable of the class B
# class instance variable in A is NOT overwritten by one in B !!!
p A.class_method2 # class instance variable of the class A

anemone with hpricot

Michał Kuklis — Mon, 11 Jan 2010 05:06:32 +0000

Anemone is a pretty cool DSL used for web crawling. I used it with Hpricot to get a feeling for what’s possible. Below is a simple example which crawls and scrappes data from a popular polish real estate website otodom:

require 'rubygems'
require 'sanitize'
require 'anemone'
require 'open-uri'
require 'hpricot'

#otodom.pl
Anemone.crawl("http://otodom.pl/index.php?mod=search&act=searchResults&qid=46911208",
{:storage => Anemone::Storage.PStore("crawl1.pstore")}) do | anemone |

# filter out useless pages
anemone.focus_crawl do |page|
page.links.delete_if do |x|
(x.to_s =~ /mod=search&act=searchResults&qid=/).nil? and
(x.to_s =~ /[a-zA-Z]+-id[0-9]*\.html$/).nil?
end
end

# process details pages
anemone.on_pages_like(/[a-zA-Z]+-id[0-9]*\.html$/) do | page |
doc = Hpricot(page.doc)
price = doc.at("//strong[@id='offerPrice']")
location = doc.at("//dl[@class='stripeMe'] > dd")
desc = doc.at("//div[@id='offerDesc'] > p")
offer_no = doc.at("//div[@id='offerFoot'] p[@class='toLeft']/span/strong")
created_at = doc.at("//div[@id='offerFoot'] p[@class='toRight']/span/strong")
photos = doc.search("//div[@id='imageList']/p/a")
end
end

blocks, procs and lambdas in ruby

Michał Kuklis — Wed, 18 Nov 2009 04:12:20 +0000

Nice post about block, procs and lambdas in ruby by Robert Sosinski.

ruby maxins in rails plugins

Michał Kuklis — Tue, 21 Jul 2009 01:16:46 +0000

Very often when looking at the code in rails plugins you can run into this:

module Taggable 
  def self.included(base)
    base.extend(ClassMethods)
  end
  module module ClassMethods
    #methods here
  end
end

This is a part of a bigger pattern which is shown below:

module ModuleA
  def self.included(base)
    # add class methods from ModuleB
    base.extend(ModuleB)
  end
end
 
module ModuleB
  def act_as_hello
    p "hello from module B"
  end
end
 
class ClassC
 #class body here
end
 
# include moduleA in classC
ClassC.send(:include, ModuleA)
 
class ClassD < ClassC
  act_as_hello
end
 
classD = ClassD.new

The pattern is used often when developing plugins with ActiveRecord. What we gain by inheriting from ClassC (class ClassD < ClassC) are instance methods from ModuleA. This is done by:

ClassC.send(:include, ModuleA)

Moreover since ModuleA is included in ClassC, ModuleA’s initializer def self.included(base) will be invoked at the time ModuleA is mixed with ClassC. The invocation will call base.extend(ModuleB). In this case base represents ClassC which will be extended by adding class methods from ModuleB. The ModuleA’s init method is shown again below:

def self.included(base)
  # add class methods from ModuleB to ClassC
  base.extend(ModuleB)
end

At the end our ClassD has now access to all class methods defined in ModuleB. act_as_hello will be called during ClassD initialization:

class ClassD < ClassC
  act_as_hello
end

Class and Instance Variables In Ruby

Michał Kuklis — Sun, 14 Jun 2009 04:27:11 +0000

nice post about class and instance vars in ruby.

few more ruby links

Michał Kuklis — Mon, 18 May 2009 23:24:42 +0000

going back to ruby again…

Michał Kuklis — Sat, 04 Apr 2009 18:05:00 +0000

Here are few links which helped me understand few ruby concepts: