To find the integer (Fixnum) values in ruby array

Question

I have an array [1, 2, "3", "4", "1a", "abc", "a"] with

• pure integers (1, 2),
• string formatted integers ("1", "2"),
• strings ("a", "b"), and
• mixed string numbers ("1a", "2s").

From this, I need to pick up only the integers (including string formatted) 1, 2, "3", "4".

First I tried with to_i:

arr = [1, 2, "3", "4", "1a", "abc", "a"]
arr.map {|x| x.to_i}
# => [1, 2, 3, 4, 1, 0, 0]

but this one converts "1a" to 1, which I don't expect.

Then I tried Integer(item):

arr.map {|x| Integer(x) }  # and it turned out to be
# => ArgumentError: invalid value for Integer(): "1a"

Now I am out of straight conversion options here. Finally, I decided to do this way, which converts the value to_i and to_s. So "1" == "1".to_i.to_s is an integer, but not "1a" == "1a".to_i.to_s and "a" == "a".to_i.to_s

arr  = arr.map do |x|
  if (x == x.to_i.to_s)
    x.to_i
  else
    x
  end
end

and

ids, names= arr.partition { |item| item.kind_of? Fixnum }

Now I got the arrays of integers and strings. Is there a simple way to do this?

Answer 1

Similar solution as provided by @maerics, but a bit slimmer:

arr.map {|x| Integer(x) rescue nil }.compact

Answer 2

I noticed most of the answer so far changes the value of "3" and "4" to actual integers.

>> array=[1, 2, "3", "4", "1a", "abc", "a", "a13344a" , 10001, 3321]
=> [1, 2, "3", "4", "1a", "abc", "a", "a13344a", 10001, 3321]
>> array.reject{|x| x.to_s[/[^0-9]/] }
=> [1, 2, "3", "4", 10001, 3321]

@OP, I have not tested my solution exhaustively, but so far it seems to work (of course its done according to provided sample ), so please test thoroughly yourself.

Answer 3

How about this?

[1,2,"3","4","1a","abc","a"].select{|x| x.to_i.to_s == x.to_s}
# => [1, 2, "3", "4"]

Answer 4

Looks pretty simple

arr.select{ |b| b.to_s =~ /\d+$/ }
# or
arr.select{ |b| b.to_s[/\d+$/] }
#=> [1, 2, "3", "4"]

Answer 5

class Array
  def to_i
    self.map {|x| begin; Integer(x); rescue; nil; end}.compact
  end
end

arr = [1, 2, "3", "4", "1a", "abc", "a"]
arr.to_i # => [1, 2, 3, 4]

Answer 6

something like this:

a = [1,2,"3","4","1a","abc","a"]



irb(main):005:0> a.find_all { |e| e.to_s =~ /^\d+$/ }.map(&:to_i)
=> [1, 2, 3, 4]

Answer 7

Hey, thanks awakening my ruby. Here is my go at this problem:

arr=[1,2,"3","4","1a","abc","a"]
arr.map {|i| i.to_s}.select {|s| s =~ /^[0-9]+$/}.map {|i| i.to_i}
//=> [1, 2, 3, 4]