From: Robert Klemme <shortcutter@...>
Date: 2012-11-18T01:10:56+09:00
Subject: Re: Alternatives to methods for large number of nested "ifs"

On Sat, Nov 17, 2012 at 2:50 PM, Philip Rhoades <phil@pricom.com.au> wrote:
> People,
>
> Thanks to the people who responded - I looked at everything but nothing
> really suited what I was trying to do but see below for some progress that I
> made and another question:

> I found that I could use sequential "ifs" instead of nested "ifs" by using
> "exit" statements in each "if" block - the script is processing incoming
> mails and can exit when a mail has been satisfactorily classified.

Ah, now we are cooking!  That looks like a proper use case for case.

>  I still
> have something like this:
>
>
> lots of code
> if block - small
> lots of code
> if block - small
> if block - large
> if block - small
> if block - large
> .
> .
> etc

For a start you could replace that with either

case email
when /foo/
  asdsdds
when /bar/
  adioaiosdipaosdpoasdopad  ads
when /something_else/
  method_which_contains_lots_of_code(email)
else
  raise "No category" # or whatever
end

Or, for more complex checks

case
when /foo/ =~ email && email.length > 1000
  d adasdsd ada
when email.urgent?
  adslkasda
else
  asdsd
end

> What I want is to be able to see the whole logic of the program in about 25
> lines (ie one screenfull of code - ie all the "if" statements) - I could
> probably use standard methods for the repetitive small "if" blocks but for
> the large "lots of code" and "if block - large" I definitely can't.  Is it
> possible that a method can be forced to NOT use local variables? - then I
> could replace the large blocks with these sorts of methods.

I am not sure I understand what you mean here.

Anyway, if you are categorizing you could use a similar approach to botp's:

CATEGORIES = [
  lambda {|email| email.size > 1000 and :large},
  lambda {|email| email.size <= 1000 and :small},
]

def categorize(email)
  CATEGORIES.each {|c| x = c[email] and return x}
  nil
end


Kind regards

robert

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