Print an array in the form of a table with Ruby

I imagine there are lots of gems available for doing this, but if you want to roll-your-own, you could do it like this, in a fairly general way:

Your input is comprised of column labels:

col_labels = { date: "Date", from: "From", subject: "Subject" }

and the data for the rows:

arr = [{date: "2014-12-01", from: "Ferdous", subject: "Homework this week"},
       {date: "2014-12-01", from: "Dajana", subject: "Keep on coding! :)"},
       {date: "2014-12-02", from: "Ariane", subject: "Re: Homework this week"}]

where col_labels and the elements of arr have the same keys.

From this point on, the code is general. First construct a hash @columns (which I've made an instance variable for convenience).

@columns = col_labels.each_with_object({}) { |(col,label),h|
  h[col] = { label: label,
             width: [arr.map { |g| g[col].size }.max, label.size].max } }
  # => {:date=>    {:label=>"Date",    :width=>10},
  #     :from=>    {:label=>"From",    :width=>7},
  #     :subject=> {:label=>"Subject", :width=>22}}

def write_header
  puts "| #{ @columns.map { |_,g| g[:label].ljust(g[:width]) }.join(' | ') } |"
end

def write_divider
  puts "+-#{ @columns.map { |_,g| "-"*g[:width] }.join("-+-") }-+"
end

def write_line(h)
  str = h.keys.map { |k| h[k].ljust(@columns[k][:width]) }.join(" | ")
  puts "| #{str} |"
end

write_divider
write_header
write_divider
arr.each { |h| write_line(h) }
write_divider

+------------+---------+------------------------+
| Date       | From    | Subject                |
+------------+---------+------------------------+
| 2014-12-01 | Ferdous | Homework this week     |
| 2014-12-01 | Dajana  | Keep on coding! :)     |
| 2014-12-02 | Ariane  | Re: Homework this week |
+------------+---------+------------------------+

If you want to reverse the display and make it a bit larger, like yours, first execute:

$_!.reverse
$_@ += 4

The easiest way to do it is with the table_print gem: http://tableprintgem.com

For example, using the array from the other answer,

your_array = [
  {date: "2014-12-01", from: "Ferdous", subject: "Homework this week"},
  {date: "2014-12-01", from: "Dajana", subject: "Keep on coding! :)"},
  {date: "2014-12-02", from: "Ariane", subject: "Re: Homework this week"},
]
tp your_array

you would get the following result:

DATE       | FROM    | SUBJECT
-----------|---------|-----------------------
2014-12-01 | Ferdous | Homework this week
2014-12-01 | Dajana  | Keep on coding! :)
2014-12-02 | Ariane  | Re: Homework this week

You can also specify the columns you want to include (as strings or symbols):

tp your_array, "subject", :from

This is very useful when your array is from an ActiveRecord query, and displaying every single column would make the output unreadable:

tp User.all, :full_name, :e-mail_address

You can even access related models:

tp User.all, :full_name, "posts.title"