gemfile.rb

  gem 'ffaker', '~> 2.1.0'

populate.rake

namespace :db do
  task :populate => :environment do
    require 'ffaker'
      20.times do|number2|
        @category.articles.create!(
         title: "Faker::Name.title}#{number2}",
         subtitle: Faker::Lorem.sentence,
         content: Faker::Lorem.paragraph
        )
      end
    end 
  end
end

seed.rb

  require 'ffaker'
# este codigo corre 3 veces y crea 3 categorias con la gema de Fakker mas suma el conteo en la variable number
  3.times do|number|
    @category = Category.create!(name: "#{FFaker::Internet.user_name}#{number}")
# esta parte crea 20 articulos por categoria agraga una variable de conteo en number2 para que no se repita el mismo titulo
    20.times do|number2|
        @category.articles.create!(
           title: "Faker::Name.title}#{number2}",
           subtitle: Faker::Lorem.sentence,
           content: Faker::Lorem.paragraph
        )
    end
  end
  
#o otra opción

seed_op2.rb

@categories = ["A","B","C"]

 @categories.each do|category|
    @category = Category.create!(name: category)
    20.times do|number2|
        @category.articles.create!(
           title: "Faker::Name.title}#{number2}",
           subtitle: Faker::Lorem.sentence,
           content: Faker::Lorem.paragraph
        )
    end
  end

seed_op3.rb

@paragraph =  [
     "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     " In purus nulla, pellentesque in lorem eget, semper faucibus dolor.",
     " Nunc sed aliquam risus, sed blandit purus.",
     " Donec at leo porttitor, varius mauris sed, tristique urna.",
     "Fusce non tincidunt lectus. Maecenas velit magna, semper ut iaculis non, dapibus vitae nisi."
   ]
@titles =  [
     "Ladipiscing elit.",
     "semper faucibus dolor.",
     "sed blandit purus.",
     "tristique urna.",
     "emper ut iaculis non, dapibus vitae nisi."
   ]
@subtitles =  [
     "Ladipiscing Ladipiscing  elit.",
     "semper Ladipiscing  faucibus dolor.",
     "vitae sed blandit purus.",
     "SGT urna.",
     "emper purus vitae nisi."
   ]
@categories = ["A","B","C"]

 @categories.each do|category|
    @category = Category.create!(name: category)
    5.times do|number2|
        @category.articles.create!(
           title: @titles.shuffle.sample,
           subtitle: @subtitles.shuffle.sample,
           content: @paragraph.shuffle.sample
        )
    end
  end