June 27, 2015
What Do You Do With an Idea? is the next Jonathan Livingston Seagull http://www.amazon.com/What-Do-You-Idea/dp/1938298071

What Do You Do With an Idea?

is the next

Jonathan Livingston Seagull

http://www.amazon.com/What-Do-You-Idea/dp/1938298071

4:48pm  |   URL: https://tmblr.co/ZTlFMx1oCY1XK
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March 14, 2013
Mongoid: Constructing multiple attribute query criteria for embedded documents.

Let us say you have the following models:

class User
  embeds_many :book_marks, :validate => false, :cascade_callbacks => true  
end

class BookMark
  field :url, type: string
  field :category, type: string # personal, work
  field :tags, type: Array    

  embedded_in :user
end

Let us say we wount to count the number of users with book marks in personal category with technology tags.

User.where(:"book_marks.category" =>  "personal", 
  :"book_marks.tags".in => ["technology"]).count

For the data set below, the query will return both rows.

name          book_marks
              category  tags
============  ========  ====              
Tom           personal  politics
              work      technology  

Jack          personal  finance
              personal  technology

We have to modify the query so that we multiple attributes of a single embedded document. MongoDB provides a construct called elem_match for such requirements.

User.where(:book_marks.elem_match => 
  { :category => "personal", :tags.in => ["technology"]).count

Now the query will only match Jack.

3:26pm  |   URL: https://tmblr.co/ZTlFMxgFeE4R
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Filed under: rails Mongoid 
March 8, 2013
Ruby assignment tricks (1.9.3)

Using an array to initialize multiple variables

>> a,b=[1,2]
=> [1, 2]
>> a
=> 1
>> b
=> 2

When the array is longer than the LHS variable count

>> a,b,c=[1,2,3,4]
=> [1, 2, 3, 4]
>> a
=> 1
>> b
=> 2
>> c
=> 3

When the array is shorter than the LHS variable count

>> a,b,c=[1,2]
=> [1, 2]
>> a
=> 1
>> b
=> 2
>> c # initialized to nil
=> nil

Using splat(*) operator at the LHS of the assignment

>> a,b,*c=[1,2,3,4]
=> [1, 2, 3, 4]
>> a
=> 1
>> b
=> 2
>> c # array containing rest of the elements
=> [3, 4]

Did you know ?

>> a = 1,2 # is same as a = [1,2]
=> [1, 2]

>> a,b=1,2 # same as a,b = [1,2]  OR a=1;b=2
=> [1, 2]
>> a
=> 1
>> b
=> 2

>> a = 1,b=2 # b is assigned to 2 but what about a?
=> [1, 2]
>> b
=> 2
>> a
=> [1, 2]

12:02am  |   URL: https://tmblr.co/ZTlFMxfmlC3w
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Filed under: ruby 
January 15, 2013
Fixing WEBrick::HTTPStatus::RequestURITooLarge exception in Rails

Add a file called webrick.rb file to the config\initializers directory.

if defined?(WEBrick::HTTPRequest)
  WEBrick::HTTPRequest.const_set("MAX_URI_LENGTH", 10240)
end

3:05pm  |   URL: https://tmblr.co/ZTlFMxbr3n2d
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July 21, 2012
Array manipulation tricks

Given array:

[1, 1, 1, 2, 3, 4, 4, 4, 4, 5, 9, 9, 9]

Desired array:

[1, 2, 3, 4, 5, 6, 7, 8, 9]

To get the desired array we need to

  • Declare the array

    a = [1, 1, 1, 2, 3, 4, 4, 4, 4, 5, 9, 9, 9]

  • Remove the two 1’s at the beginning of the array.

    a[0..1] = [] # => [1, 2, 3, 4, 4, 4, 4, 5, 9, 9, 9]

  • Remove three 4’s in the middle of the array.

    a[3..5] = [] # => [1, 2, 3, 4, 5, 9, 9, 9]

  • Insert 6, 7, 8 to the middle of the array.

    a[5..0] = [6,7,8] # => [1, 2, 3, 4, 5, 6, 7, 8, 9, 9, 9]

  • Remove the two 9’s at the end of the array.

    a[-2..-1] = [] # => [1, 2, 3, 4, 5, 6, 7, 8, 9]

Interesting tricks:

  • Inserting using 0 terminated range

    a[5..0] = [6,7,8]

    When the range is terminated by a 0, the RHS value is inserted to the array at the index specified by the beginning of the range.

  • Removing items from the tail

    Following syntax will not work:

    a[-1..-2] = []

    This is because the range -1..-2 is an empty range(just like the range 2..1).

    (-1..-2).to_a # => []

    In a valid range, the starting number should be smaller than the ending number. The number -2 is smaller than the number -1. Hence the range is written as -2..-1.

    (-2..-1).to_a # => [-2, -1]

10:31pm  |   URL: https://tmblr.co/ZTlFMxPrAOTG
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Filed under: ruby array 
July 16, 2012
"Demanding you want something you clearly have no power to get is losing."

— Josh Marshal . ( PS: I have modified the original quote by replacing the word Saying; at the beginning of the sentence; with the word Demanding.)

2:29pm  |   URL: https://tmblr.co/ZTlFMxPTszE2
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Filed under: quote 
July 11, 2012
Ruby implementation for Conway’s game of life

Here is my implementation for Conway’s game of life

https://gist.github.com/3092214

3:05pm  |   URL: https://tmblr.co/ZTlFMxP8ul_W
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June 28, 2012
Polymorphic and STI models working together in Mongoid

Here is an example of polymorphic and STI models working together:

class User
  include Mongoid::Document

  embeds_many :phones, :as => :identifiable
  embeds_many :emails, :as => :identifiable
  embeds_many :social_profiles, :as => :identifiable

  field :first_name, type: String
  field :middle_name, type: String
  field :last_name, type: String
  field :email, type: String
  field :password, type: String
end

class Identifier
  include Mongoid::Document
  embedded_in :identifiable, polymorphic: true  
  field :name, type: String # work, home, linked_in etc
  field :valid, type: Boolean
  field :validated_at, type: DateTime
end

class Email < Identifier
  field :email, type: String
end

class Phone < Identifier
  field :phone, type: String
end

class SocialProfile < Identifier
  field :url, type: String
end

6:55pm  |   URL: https://tmblr.co/ZTlFMxOJkPjB
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Filed under: rails mongoid STI polymorphic 
June 20, 2012
Installing rmagick on Windows 7(64bit) + Ruby 1.9.3p194

Prerequisites:

Steps:

  • Download Win32 dynamic at 16 bits-per-pixel bundle. Do not use the 64 bit bundle.
  • Install the bundle to a directory without spaces (e.g., C:\ImageMagick). Select the option for the header files during installation.

  • Add ImageMagick exe directory to path(e.g., C:\imagemagick\ImageMagick-6.7.7-Q16). Read this article to find out how to set PATH.

  • Check ImageMagick installation: Launch a new command shell and check the location of the identify command.

    where identify

  • Install the rmagick gem ( notice the forward slash)

    gem install rmagick  -- --with-opt-dir=C:/imagemagick/ImageMagick-6.7.7-Q16

Reference

4:10pm  |   URL: https://tmblr.co/ZTlFMxNnKa4z
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Filed under: rmagick ruby windows rails 
June 20, 2012
Segfault issues while running `thin` server on Windows + Ruby 1.9.3 + eventmachine-1.0.0.rc.1

The issue is dicussed at length at github. Here is a temporary fix:

Clone the git repo

git clone https://github.com/eventmachine/eventmachine.git
cd eventmachine/ext

Edit extconf.rb and paste the following lines at line 103

found = RbConfig::CONFIG.values_at("CFLAGS", "CPPFLAGS").any? { |v| v.include?("FD_SETSIZE") }
$defs.push "-DFD_SETSIZE=32767" unless found

Install the gem using the cloned+modified repo

cd ..
gem build eventmachine.gemspec
gem install eventmachine-1.0.0.rc.1.gem

Run the thin server in project directory

thin start

2:34am  |   URL: https://tmblr.co/ZTlFMxNlQOLZ
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Filed under: rails thin eventmachine windows 
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