01-Studio-20 - lesson

Studio20-Lesson1.rb

#####
##    The following lines load the files we need, and also 
##    makes sure everything is in place

['../results', '../html'].each do |dir|
  raise "#{dir} does not exist as expected" if !File.exists?(dir)
end

require 'rubygems'
require 'rest-client'
require 'crack'
require 'pp'
#####





#################################

#####    00
Kernel.puts("hello world")


##################################
#####   00.5
#####   Variables, strings and assignment

##    The words on the left represent a variable. It's just an *arbitrary* label
##    that we make up to point to some data that we want to reference later

##    The data in this case is the String, "Hello World"
##    The main, and essential difference, is that one has quotation marks around it, and the other doesn't
hello_world = "Hello world, in a variable"

##    Also, note what the equals sign does here. It is assigning what's on the right to the variable
##    on the left. It only goes one way. You can't, for instance, do this:
##    "Hello world string " = hello_world

##    Try changing the value of hello_world, and outputting it. See what happens when you don't
##    enclose the String with quotation marks
#! Kernel.puts(hello_world)

##    Main takeaway: Strings, these characters wrapped up in double quotes, are data
##    Variables, and other words NOT in quotation marks, are how we tell Ruby what we're
##      referencing. In terms of variables, Ruby doesn't care what we name them
##      just as long as we're consistent in referring to them





=begin
#################################

#####    01
## Files to load

test_filename = "http://code-dancow.s3.amazonaws.com/studio20/tweets-test/tweets-jayrosen_nyu-page_1.xml"
##    There's actually 16 of these files. You can replace '1' with any of those numbers

##    This command downloads the test_filename
test_file = RestClient.get(test_filename)


## lets print it out
#! Kernel.puts test_file

##    Here's some explanation: "puts" is a method. So is "RestClient.get"
##    More specifically, 'get' is a method that belongs to 'RestClient'
##    The dot is what invokes 'get'
##
##    Similarily, 'puts' is a method that belongs to the object 'Kernel'
##    And 'puts' prints out to screen
##
##    But to save us a little typing, you can just do puts "whatever_your_string is"
##    Kernel is, for our purposes, a ubiquitous object. The interpreter will assume we
##    are referring to it if we just through 'puts' out there on its own
##      so:

#!    puts( "Hello World")

##
##    What did "RestClient.get" do? We saved it in a variable called test_file. Try doing puts on that
##
#!    puts( test_file)
=end




=begin
#################################

#####    02
#####   Parsing the XML

##    This command parses it into a usable data structure
parsed_test_file = Crack::XML.parse(test_file)

##    pp is a command that, like puts, prints to screen
##    but does so in a prettier format (it's short for 'pretty-print')
#
##     let's see what test_file looks like
#! pp parsed_test_file

##    Let's count how many statuses there are
#! puts parsed_test_file['statuses'].length

##    Let's make a nicer output
##    put it in a temporary


#! puts "There are " + parsed_test_file["statuses"].length.to_s + " statuses in the file: " + test_filename 

##    Try taking out the .to_s; what happens?

##    So far, the main datatype that we've played around with are Strings
##    Here are two new ones: Numbers and Arrays. We'll get to Arrays in the next section
##
##    But numbers are as simple as you think. However, they are NOT set off by quotation marks
##    Or any other kind of symbol. In fact, if you put them inside of quotation marks, they are
##    nothing but strings. And you can't add Strings and Numbers together...and for the most part
##    you can't add data of different types together without some kind of error or something unexpected
##    happening...


=end






=begin
#################################

#####   03
#####   Looping through the file

##    Make a variable to hold that long name
statuses = parsed_test_file['statuses']

##    As you might guess, 'statuses' essentially contains all the tweets from the page we downloaded
##    'statuses' is more than just a single object, it's a series/list of them. This is an Array

##    Read more about Ruby Arrays:
##    

##    We can use the keys method to see what exists in each status
#! pp statuses.first

## You should get something like this
#	{"coordinates"=>nil,
#	 "created_at"=>"Fri Mar 25 22:17:42 +0000 2011",
#	 "truncated"=>"false",
#	 "favorited"=>"false",
#	 "entities"=>
#	  {"urls"=>
#	    {"url"=>
#	      {"expanded_url"=>nil,
#	       "url"=>"http://bit.ly/gueC4z",
#	       "end"=>"94",
#	       "start"=>"74"}},
#	   "hashtags"=>nil,
#	   "user_mentions"=>nil},
#	 "text"=>
#	  "Help veterans get jobs. We already know they can handle workplace stress. http://bit.ly/gueC4z",
#	 "contributors"=>nil,
#	 "id"=>"51407434866098176",
#	 "retweet_count"=>"100+",
#	 "geo"=>nil,
#	 "retweeted"=>"false",
#	 "in_reply_to_user_id"=>nil,
#	 "source"=>"web",
#	 "in_reply_to_screen_name"=>nil,
#	 "user"=>{"id"=>"16303106"},
#	 "place"=>nil,
#	 "in_reply_to_status_id"=>nil}

##    Let's loop through each status. Using the bracket['string'] notation, we can 
##    pick out any attributes we want

statuses.each do |status|
#!  puts( status['text'])
#!  puts( status['retweet_count'])
end

=end



=begin
#################################

#####   04
#####   Writing to our hard disk

##    So far, nothing we've done has been saved permanently
##    Now we'll run through some commands to write files
output_xml_file = File.open('../results/some_tweets.xml', 'w')


##    Remember that 'test_file' was the variable we used to store the saved file
output_xml_file.write(test_file)


##    Let's open a different file
output_file = File.open('../results/parsed_tweets.html', 'w')

##    We're going to write some HTML
##    
output_file.puts('<html><head>')
output_file.puts('<link rel="stylesheet" href="../html/styles.css" type="text/css" media="screen" />')
output_file.puts('</head><body>')

####    Note how the File class has its own puts method
####    which sends to the string to the file



##    Let's do that loop we did in Step 04
statuses.each do |status|
  output_file.puts('<div class="box">')
  output_file.puts('<p>'+ status['text'] + '</p>')
  output_file.puts('</div>')
end


output_file.puts('</body></html>')
=end