Formatting data array with ruby

Question

I am trying to get data from PostgreSQL with ruby and store them into an array, for that I have a small script:

Script :

require 'pg'  

conn=PGconn.connect( :hostaddr=>"192.168.111.136", :port=>5432, :dbname=>"sentinel_poc",:user=>"sdn_mehdi", :password=>'skyline123')  

res = conn.exec("SELECT dns_name FROM dns_table group by dns_name").to_a  

a_dns = []  

res.each { |r| a_dns << r }  
puts a_dns.join(",")

The outcome is :

{"dns_name"=>"youtube.com                                       "},{"dns_name"=>"stackoverflow.com                                         "},{"dns_name"=>"cisco.com                                         "},{"dns_name"=>"facebook.com                                      "},{"dns_name"=>"yahoo.com                                         "},{"dns_name"=>"onf.com                                           "},{"dns_name"=>"safe.com                                          "},{"dns_name"=>"linkedin.com                                      "},{"dns_name"=>"amazon.com                                        "},{"dns_name"=>"google.com                                        "},{"dns_name"=>"java.com                                          "},{"dns_name"=>"live.com                                          "},{"dns_name"=>"rails.com                                         "},{"dns_name"=>"postgresql.com                                    "},{"dns_name"=>"hp.com                                            "},{"dns_name"=>"wikipedia.org                                     "}

What I need is just the name of each domain name! Something like {"youtube.com","google.com","java.com","rails.com","hp.com"}

Any suggestions would be greatly appreciated.

The result you expect ({"youtube.com","google.com",...}) cannot exist in Rails, it looks like a Hash but with only keys (or values?). Did you mean something like an array of the dns names? or an array of hashes containing :dns_name => string_of_dns_name ? — MrYoshiji
– MrYoshiji, Commented Apr 10, 2014 at 13:20

Arup Rakshit · Accepted Answer · 2014-04-10 13:17:58Z

3

I think you need :

res.flat_map(&:values)
# or if you have hashes having size more then 1, then use the below
res.map { |h| h["dns_name"] }
# to strip leading and trailing whit spaces
res.map { |h| h["dns_name"].strip }

edited Apr 10, 2014 at 13:17

answered Apr 10, 2014 at 13:09

Arup Rakshit

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3 Comments

Magnuss Over a year ago

@midobAck Please be more specific, what doesn't work?

midobAck Over a year ago

I tried all your suggestions but I get the same outcome as before !

Arup Rakshit Over a year ago

@midobAck Got your point.. do res.map! { |h| h["dns_name"].strip }

Alok Anand · Accepted Answer · 2014-04-10 14:13:31Z

0

Taking your code only, and doing small changes, I guess following will work for you

a_dns = []  

res.each { |r| a_dns << r.values[0].strip }  
puts a_dns

answered Apr 10, 2014 at 14:13

Alok Anand

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