# Where should I put the loops

**URL:** <https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350>\
**Category:** Ruby\
**Created:** [July 17, 2008, 4:52pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350 "2008-07-17T16:52:13Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [July 17, 2008, 4:52pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350/1 "2008-07-17T16:52:13Z")

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Hi all,

I try to write a script to fecth some webpages from the internet, parse  
the webpages and write them into csv format file.

Here are the formats of webpages:  
website…A001  
…  
website…A101

website…B001  
…  
website…B401

website…Z001  
…  
website…Z301

I use two loops to do the job. 1) one loop is to iterate from letter A  
to Z,  
which I have it done by iterate an array containing letter A to Z.  
2) another loop is to iterate the number from 1 to whatever numbers I  
prefer (or using a while loop).

If I write the script in a procedural way I have no problem at all but  
they look kind of ugly. Now I try to rewrite them with OOP method. My  
confusion here is that where should I write the loops: in the main  
scripts and define a method for them and call the method in the main  
scripts?

Thanks,

Li

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<div class="post-metadata">

**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [July 17, 2008, 6:11pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350/2 "2008-07-17T18:11:42Z")

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What you can do is write three loops so

[A…Z].each do |letter|  
[1…num].each do |number|  
#Process the website in here  
process\_website letter number  
end  
end

As for OOP you could have a Parse class and in and a AppRunner class  
(which  
holds all the websites). the process\_website would be in the AppRunner  
class  
and would create a new parser for each website, parse the website and  
then  
either if the websites are indepent (have the parse take care of the  
writing  
to csv), or if dependent in some manner (have the AppRunner write to  
cvs)

Reuben Doetsch

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<div class="post-metadata">

**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [July 21, 2008, 3:31pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350/3 "2008-07-21T15:31:20Z")

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reuben doetsch wrote:

> What you can do is write three loops so
> 
> [A…Z].each do |letter|  
> [1…num].each do |number|  
> #Process the website in here  
> process\_website letter number  
> end  
> end

Hi Reuben,

Thank you very much for the neat script. I have another question:  
within the nested loop the maximum num is not fixed, for example, there  
are A001-A201 for letter A and B001-B333 for letter B… And most of  
the time I don’t know what is the maximum page I can fetch for each  
letter. But I know if the page doesn’t exit that Ruby will fetch the  
same papge again and again until it comes to the upper limit of loop. In  
order to break out of the loop what I do is that I compare the website  
address of current page and the previous page. If they are the same I am  
going to break out the current loop and go to next letter. I wonder how  
you implement this idea into the current script.

Thanks,

Li

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<div class="post-metadata">

**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [July 21, 2008, 11:10pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350/4 "2008-07-21T23:10:23Z")

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Kaldrenon wrote:

> This is assuming that the only time you will ever have duplication is  
> when you have reached the end of the loop for a given letter. Is that  
> correct?

Thank you very much. The code really cool.

Li

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<div class="post-metadata">

**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [July 21, 2008, 6:50pm UTC](https://www.ruby-forum.com/t/where-should-i-put-the-loops/143350/5 "2008-07-21T18:50:37Z")

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On Jul 21, 9:25 am, Li Chen [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > [A…Z].each do |letter|  
> > [1…num].each do |number|  
> > #Process the website in here  
> > process\_website letter number  
> > end  
> > end

> In order to break out of the loop what I do is that I compare the website  
> address of current page and the previous page. If they are the same I am  
> going to break out the current loop and go to next letter. I wonder how  
> you implement this idea into the current script.

If I understand what you’re asking correctly, it would be something  
like this (this is pseudo-code)

[A…Z].each do |letter|  
old\_website = nil  
[1…num].each do |number|  
#Process the website in here  
new\_website = fetch\_website(letter, number)  
if new\_website != old\_website  
process\_website(new\_website)  
else  
#break out of num-loop  
end  
old\_website = new\_website  
end  
end

This is assuming that the only time you will ever have duplication is  
when you have reached the end of the loop for a given letter. Is that  
correct?