Re: Ruby Newbie...Classes and Objects, oh my!

On 24.05.2010 18:42, fuglyducky wrote:
> On May 24, 8:57 am, Robert Dober <[e-mail]> wrote:
>> On Mon, May 24, 2010 at 4:30 PM, fuglyducky <[e-mail]> wrote:
>>> I'm very new to Ruby and I'm trying to create a program that will take
>>> one text file and dump each line into an array. Then I take a second
>>> file and dump that into a string. Then I insert the string into the
>>> array. The code for these pieces work. However, for flexibility I want/
>>> need to be able to use OO methods and that is where I seem to hit a
>>> wall. Not sure what I am supposed to do or how to call it. Below is my
>>> code, any input you may have would be greatly appreciated!!!
>>> ###############################################################
>>> class XMLProcessing
>>>        def initialize(array_file, string_file, output_file)
>>>                @array_file = array_file
>>>                @string_file = string_file
>>>                @output_file = output_file
>>>        end
>>>        def lines_to_array
>>>                # Dump each line from text file into array
>>>                File.open(@array_file).each do |line|
>>>                        my_array << line
>> This is a local variable, uninitialized for that matter
>> try
>>       @my_array = []
>>       File.open...
>>               @my_array << line
>>       end
>>
>> However, you could also simply do a
>>      @my_array = File.readlines( @array_file ).map( &:chomp )
>> or the more explicit (and in Rubies < 1.9 necessary )
>>      @my_array = File.readlines( @array_file ).map{ |line| line.chomp }>                end
>>>        end
>>>        def file_to_string
>>>                # Create string from text file
>>>                @my_string_file = File.open(@string_file)
>>>                my_string = @my_string_file.read
>> Same here
>>              @my_string = ...
>>
>>>        end
>>>        def string_into_array
>>>                # Insert string into array
>>>                my_array.insert((my_array.length - 1), my_string)
>> and here too
>> @my_array>        end
>>
>>>        def new_array_to_file
>>>                # Dump the array to a text file
>>>                newFile = File.new(@output_file, "w+")
>>>                my_array.each { |element| newFile.puts element }
>> change here too
>>            @my_array
>>
>>>                print 'New file created: ' + (@output_file)
>>>        end
>>> end
>>> stat_xml = XMLProcessing.new("Stat.Template.xml", "Seg.Template.xml",
>>> "stat.xml.txt")
>> Now just call the methods you want to execute on stat_xml as e.g.
>> stat_xml.file_to_string
>> ..
>> ..
>>
>> I do not think your design is ideal, calling all those external method
>> calls for intermediate computations(1), but for a beginner it is
>> pretty nicely structured code.
>>
>> HTH
>> R.
>>
>> (1) But there might be reasons invisible to YHS.
>>
>>
>>
>>> ###############################################################
>> --
>> The best way to predict the future is to invent it.
>> -- Alan Kay
> 
> Wow...thanks for the response!!! I'm not a programmer for a developer
> by any means. I'm a tester that needed a quick (and hopefully not too
> dirty) way of creating the files I need. The reason I wanted to call
> all of the submethods was because I need to be able to create a random
> number of some of the individual files before I dump them into the
> array. I thought that in the main body of the code I would script it
> out to call that particular method. This is all pretty new to me...is
> that bad form?

Hm, difficult where to start.  If I read your code properly you have 
three file names as inputs and want to create the concatenation of the 
two first files as the third file.  On shell level you could simply do

$ cat f1 f2 > f3

There is no Ruby programming needed.  Even if you want to do that in 
Ruby, there is not really a need for new classes you can do this in just 
a few lines in a function.

# Concat all files given as second, third etc. argument
# to a file with name provided as first argument
def file_concat(out, *in)
   File.open out, "w" do |io|
     in.each do |file_in|
       File.foreach file_in do |line|
         io.puts line
       end
     end
   end
end

file_concat("stat.xml.txt", "Stat.Template.xml", "Seg.Template.xml")

This code has the advantage over your solution with the Array that it 
easily processes arbitrarily large files because you do not have to hold 
the complete output file in memory.

A new class of your own is probably only worthwhile if you have to do 
more complex processing on the file's content.  Even if you create a 
class you should do the processing like shown in the first example, i.e. 
not hold the complete files in memory, e.g.

class XMLProcessing
	def initialize(array_file, string_file, output_file)
		@array_file = array_file
		@string_file = string_file
		@output_file = output_file
	end

   def process
     File.open @output_file, "w" do |io|
       [@array_file, @string_file].each do |file_in|
         File.foreach file_in do |line|
           io.puts line
         end
       end
     end
   end
end


Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/