Re: Alternatives to methods for large number of nested "ifs"

Ruby
1

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:

On 2012-11-17 01:35, Philip R. wrote:

if …
it to something like:
call something
the same position in the nested “ifs”?
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. 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

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.

Thanks,

Phil.

–
Philip R.

GPO Box 3411
Sydney NSW 2001
Australia
E-mail: [email protected]

2

On Sat, Nov 17, 2012 at 2:50 PM, Philip R. [email protected]
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.

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

3

On 2012-11-18 00:50, Philip R. wrote:

I have an existing script that looks like:
some lines of code
.
if …
I found that I could use sequential “ifs” instead of nested “ifs” by
if block - small
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.

procs were the solution (they allow shared variables) - I now have this
at the end of the program:

                             ####        Mailing-List:,

Delivered-To: and Reply-To: lines
p_mailing_list.call
#### OK line_To non-blocked domains
p_line_To_non_blocked_domains.call
#### OK in_mailing_list
p_in_mailing_list.call
#### Drop in_black_list_to
p_in_black_list_to.call
#### Drop in_black_list_from AND
!Srejector content
p_in_black_list_from.call
#### Drop Bounce Bounced - deleting
old quarantined file if it exists
p_bounce_bounced.call
#### Reject LinkedIn invitation
p_LinkedIn.call
#### OK Srejector content -
incoming/outgoing
p_Srejector.call
#### OK in_domains_list - for
incoming/outgoing mails, system mails etc
p_in_domains_list.call
#### OK put me on your whitelist
subject
p_put_me_on_your_whitelist_subject.call
#### OK To: line
p_line_To.call
#### Drop !in_white_list_to
p_not_in_white_list_to.call
#### Drop !in_white_list_to_substr
p_not_in_white_list_to_substr.call
#### OK in_white_list_from
p_in_white_list_from.call
#### Drop in_subject_list
p_in_subject_list.call
#### Reject !in_white_list_from
p_not_in_white_list_from.call
#### OK shouldn’t get here?
p_shouldnt_get_here.call

Regards,

Phil.

–
Philip R.

GPO Box 3411
Sydney NSW 2001
Australia
E-mail: [email protected]