How to remove duplicates in a hash in Ruby on Rails?

Question

I have a hash like so:

[
  {
    :lname => \"Brown\",
    :email => \"james@intuit.com\",
    :fname => \"James\"
  },
  {
    :lname => nil,
            


        

Answer 1

Ok, this (delete duplicates) is what you asked for:

a.sort_by { |e| e[:email] }.inject([]) { |m,e| m.last.nil? ? [e] : m.last[:email] == e[:email] ? m : m << e }

But I think this (merge values) is what you want:

a.sort_by { |e| e[:email] }.inject([]) { |m,e| m.last.nil? ? [e] : m.last[:email] == e[:email] ? (m.last.merge!(e) { |k,o,n| o || n }; m) : m << e }

Perhaps I'm stretching the one-liner idea a bit unreasonably, so with different formatting and a test case:

Aiko:so ross$ cat mergedups
require 'pp'

a = [{:fname=>"James", :lname=>"Brown", :email=>"james@intuit.com"},
     {:fname=>nil,     :lname=>nil,     :email=>"brad@intuit.com"},
     {:fname=>"Brad",  :lname=>"Smith", :email=>"brad@intuit.com"},
     {:fname=>nil,     :lname=>nil,     :email=>"brad@intuit.com"},
     {:fname=>"Brad",  :lname=>"Smith", :email=>"brad@intuit.com"},
     {:fname=>"Brad",  :lname=>"Smith", :email=>"brad@intuit.com"}]

pp(
  a.sort_by { |e| e[:email] }.inject([]) do |m,e|
    m.last.nil? ? [e] :
      m.last[:email] == e[:email] ? (m.last.merge!(e) { |k,o,n| o || n }; m) :
        m << e
  end
)
Aiko:so ross$ ruby mergedups
[{:email=>"brad@intuit.com", :fname=>"Brad", :lname=>"Smith"},
 {:email=>"james@intuit.com", :fname=>"James", :lname=>"Brown"}]

Answer 2

In Ruby 1.9.2, Array#uniq will accept a block paramater which it will use when comparing your objects:

arrays.uniq { |h| h[:email] }

Answer 3

I know this is an old thread, but Rails has a method on 'Enumerable' called 'index_by' which can be handy in this case:

list = [
  {
    :lname => "Brown",
    :email => "james@intuit.com",
    :fname => "James"
  },
  {
    :lname => nil,
    :email => "brad@intuit.com",
    :fname => nil
  },
  {
    :lname => "Smith",
    :email => "brad@intuit.com",
    :fname => "Brad"
  },
  {
    :lname => nil,
    :email => "brad@intuit.com",
    :fname => nil
  },
  {
    :lname => "Smith",
    :email => "brad@intuit.com",
    :fname => "Brad"
  },
  {
    :lname => nil,
    :email => "brad@intuit.com",
    :fname => nil
  }
]

Now you can get the unique rows as follows:

list.index_by {|r| r[:email]}.values

To merge the rows with the same email id.

list.group_by{|r| r[:email]}.map do |k, v|
  v.inject({}) { |r, h| r.merge(h){ |key, o, n| o || n } }
end

Custom but efficient method:

list.inject({}) do |r, h| 
  (r[h[:email]] ||= {}).merge!(h){ |key, old, new| old || new }
  r
end.values

Answer 4

If you're putting this directly into the database, just use validates_uniqueness_of :email in your model. See the documentation for this.

If you need to remove them from the actual hash before being used then do:

emails = []  # This is a temporary array, not your results. The results are still in my_array
my_array.delete_if do |item|
  if emails.include? item[:email]
    true
  else
    emails << item[:email]
    false
  end
end

UPDATE:

This will merge the contents of duplicate entries

merged_list = {}
my_array.each do |item|
  if merged_list.has_key? item[:email]
    merged_list[item.email].merge! item
  else
    merged_list[item.email] = item
  end
end
my_array = merged_list.collect { |k, v| v }