Question

I have 2 multi selectors in extJS (respondents groups and jsut respondents). Erery respondent have a group (ONLY 1).

here, how i selected my ids …

I get respondent_group id, for example = 1

  respondent_ids       = params[:selected_respondents].split(/,/).collect {|r| r.to_i}

here i get respondents ids: 3,4,1

  respondent_pure_ids  = params[:selected_alone_respondents].split(/,/).collect {|r| r.to_i}

here i find respondents in group (for example i have 10 groups, every group has 1-3 respondents).

  respondents       = Respondent.find(:all, :conditions => ["respondent_group_id in (?) AND id NOT IN (?)", respondent_ids, session[:user].id]) 

I find respondents .

  respondents_alone = Respondent.find(:all, :conditions => ["id in (?) AND id NOT IN (?)", respondent_pure_ids, session[:user].id]) 

here i found respondents (i find id where respondent_group = ?) and send them email.

        respondents.each do |r|
            Notifier.deliver_inquiry_notification() 
        end

What I want?
I get respondents and respondents_alone id’s.

For example respondents = 3 , 4 , 6
respondents_ alone = 3, 5, 6, 8

I have 3 and 6 ids in both. I dont want to dublicate my data . How to check: if respondents ids DOES NOT equals respondent_alone ids I SEND EMAIL else error!

Answer 1

You can use ruby array arithmetic to get the difference between both arrays or to get every entry only once:

a = [3, 4, 6]
b = [3, 5, 6, 8]
a - b # [4] (only a without any element of b, difference)
b - a # [5, 8] (only b without any element of a, difference)
a | b # [3, 4, 6, 5, 8] (complete set of all ids, union)
a & b # [3, 6] (ids same in both arrays, intersection)

With this you can check if some ids are only in one array or in both, e.g. difference is empty or a|b==a&b => both are equal

cf. http://www.ruby-doc.org/core/classes/Array.html