Find any pairs of numbers in a sequence that add up to sum N

output.txt

#### OUTPUT
1
  Enter comma seperated integers
  1,2,3,4,6,7,8
  Enter pair sum
  10
  ((2, 8), (3, 7), (4, 6), (6, 4), (7, 3), (8, 2))
  
2
  Enter comma seperated integers
  1,2,3,4,6,7,8
  Enter pair sum
  5
  ((1, 4), (2, 3), (3, 2), (4, 1))
  
3
  Enter comma seperated integers
  1,2,3,4,6,7,8
  Enter pair sum
  20
  (No pairs)
  
4
  Enter comma seperated integers
  1,2,3,4,6,7,p
  Invalid Input (Only Integers allowed)
  

pairs_1.rb

	# Find any pairs of numbers in a sequence that add up to sum N.
# Given input 1, 8, 2, 3, 5, 7
# Expected Output (8,2), (3, 7)

# Accept numbers and store it into array
# Take one element from array and compare it to rest of the elements
# to find resulting element

class CheckPairs 
    #  Base class to instantiate utility class
    def find_pairs
        nums, sum = user_input
        num_pairs = NumPairs.new(nums, sum)
        pairs = num_pairs.get_pairs
        format_output(pairs)
    end

    def user_input # Takes user input and returns to calling function as arrays
        p 'Enter comma seperated integers'
        nums = gets.chomp
        if nums.split(',').join('').scan(/\D/).empty?
            p 'Enter pair sum'
            sum = gets.chomp.to_i
            return [nums, sum]
        else
            p 'Invalid Input (Only Integers allowed)' 
            exit
        end
    end

    def format_output(output) # convert array to string and replace [ ] with ( )
        return p '(No pairs)' if output.empty?
        output = output.to_s
        output = output.tr('[','(').tr(']',')')
        p output
    end 
end

class NumPairs
    # Utility class to perform required functions
    def initialize(numbers, sum) # Initialize numbers and sum
        @numbers = numbers.split(',').map(&:to_i).uniq
        @sum = sum.to_i
    end

    def get_pairs
        pairs_array = []
        @numbers.each do |num|
            temp_array = @numbers.reject { |a| a == num }
            pairs_array << pairs(num,temp_array)
        end
        pairs_array.flatten(1).uniq
    end

    def pairs(num, my_array)
        pairs = []
        my_array.each do |a|
            pairs << [num, a] if check_sum(num, a)
        end
        pairs
    end

    def check_sum(num1, num2)
        return true if num1 + num2 == @sum
    end
end

pairs = CheckPairs.new
pairs.find_pairs