find, sql in ; select detect partition concat gsub split

http://www.1keydata.com/sql/sqlin.html
http://www.rubyinside.com/clever-find-conditions-in-rails-without-sql-56.html
list = [1,2]
User.find(:all, :conditions => {:id => list, :staus => 'health'})
User.find(:all, :conditions => ["follows_counter =0 and id In (?)",list])

SELECT * FROM `users` WHERE (`users`.`id` IN (1,2))

---

http://www.ruby-doc.org/core/classes/Enumerable.html#M003154
#把參數處理成 array
emails = params[:email].gsub(/\s/, "").gsub(/;/, ",").split(/,/)

in_email_users = User.find(:all, :conditions => {:nickname => emails })
in_email = in_email_users.map(&:nickname)

#就像是兩個回圈下去跑
out_emails = emails.select { |e| !in_email.detect{|i| i == e } }

#email 的驗證 regular expression
out_emails, wrong_emails = out_emails.partition { |e|
e =~ /^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/
}

out_emails.concat(in_email)

---

>> (1..20).select {|i| i % 5 == 0 }
=> [5, 10, 15, 20]
>> (1..20).detect {|i| i % 5 == 0 }
=> 5