_show_details.html.erb

<%= some_text("LOCATION1") %>
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application_helper.rb

module ApplicationHelper
  def some_text(loc)
    if Constants::SOME_LOCATIONS.include?(loc)
      "This is a valid location"
    else
      "This is not a valid location"
    end
  end
end

contants.rb

module Constants
  SOME_LOCATIONS = ["LOCATION1","LOCATION2"]
end