From: James Coglan <jcoglan@...>
Date: 2009-07-10T19:56:56+09:00
Subject: Re: Question about ruby syntax

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> I don't understand this code. I can see that it is a block  that returns
> array of entries containing  the html for every tr with a white
> background
>
>  #################################
>
> page.search("//tr[@bgcolor='#ffffff']")  do |row|
>
> from, subject = *row.search("//b/text()")
> url = page.uri.to_s.sub(/ui.*$/,
> row.search("//a").first.attributes["href"])
> puts "From: #{from}\nSubject: #{subject}\nLink: #{url}\n\n"
>
> email = agent.get url
>
>
> ##################################
>
>
> But what does the   from, subject = *row.search("//b/text()")  do?


The `*` performs what's called a destructuring binding. This expression
takes the array returned by `row.search("//b/text()")` and assigns one
member to each variable listed on the left hand side. It's equivalent to:

temp = row.search("//b/text()")
from = temp[0]
subject = temp[1]


Finally what does this do? I can see a regex but don't understand the
> line.
>
> url = page.uri.to_s.sub(/ui.*$/,
> row.search("//a").first.attributes["href"])


The expression `row.search("//a").first.attributes["href"]` finds the first
<a> element in the row and gets its `href` attribute, which I imagine will
be a string containing a URL. So this is basically just:

url = page.uri.to_s.sub(/ui.*$/, "SOME_URL")

So it takes the page's URI, casts it to a string (to_s) and replaces the
pattern /ui.*$/ with the `href` from an anchor tag.

--
James Coglan
http://jcoglan.com

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