Question

I have a RoR app that does a join between multiple tables and returns the resultset as json back to the client.
I need help in figuring out how to send unique column values only.
For e.g., if you have an employee and department table, doing a join on the two would return:

Physics   John   
Physics   Joe
Math      Charlie
Math      Sheila

How can I return data back to the client that removes duplicate values, for e.g.

Physics => { John, Joe }
Math = > { charlie, Sheila }

I want to reduce unnecessary sending of duplicate data over the wire.

Any thoughts?

EDIT:

Changed it to this (found it on stack overflow) and it worked:

@lec_hash = @lectures.inject({}) do | result, row |
    result[row.subject] = [] if result[row.subject].nil?
    result[row.subject] << row.name
    result
end

Answer 1

Prepare a hash where key is your subject name and value is array of names opted the subject

hash = Hash.new {|h,k| h[k] = [] }
result.each do |row|
  hash[ row.subject]  << row.name
end

Assumptions : result is array of AR records and model has subject and name(person’s name) attribute(column)

and then convert hash.to_json