How to generate a random String in Ruby?

In this article, we will learn how to generate a random String in Ruby.

Approach to generate a random String in Ruby:

When you need to generate a random alphanumeric string of a specified length in Ruby, you have a couple of options.

If you are using Ruby version >= 2.5, Ruby, you can simply go with:

SecureRandom.alphanumeric(length)

For older versions, you can utilize a little numeric conversion hack: integer#to_s method accepts an argument representing the base.

For example:

13.to_s(2) # = “1101” in binary
13.to_s(16) # = “d” in hex

Custom String generator:

Ruby

class Generator
  # Define CHARSET by merging character ranges 
  # and converting them to arrays
  CHARSET = [('0'..'9'), ('a'..'z'), ('A'..'Z')].flat_map(&:to_a)

  # Constructor method to initialize 
  # the Generator object
  def initialize(length:, exceptions: [])
    @length = length
    
    # Create allowed_charset by removing 
    # exception characters from CHARSET
    @allowed_charset = CHARSET - exceptions
  end

  # Method to generate a random string of 
  # specified length using the allowed character set
  def perform
    
    # Generate an array of length @length, 
    # where each element is a random 
    # character from @allowed_charset
    random_string = Array.new(@length) { @allowed_charset.sample }
    
    # Join the array elements to form 
    # a single string and return it
    random_string.join
  end
end

# Create an instance of Generator with 
# length 10 and exceptions for characters
# that might be confused
generator = Generator.new(length: 10, exceptions: ['1', 'I', 'l', '0', 'o', 'O'])

# Generate and print a single random string
puts generator.perform

# Create another instance of Generator 
# with the same specifications
better_generator = Generator.new(length: 10, exceptions: ['1', 'I', 'l', '0', 'o', 'O'])

# Generate an array of 3 random 
# strings and print them
puts (1..3).map { better_generator.perform }

Output

YLVvEEqmYi
ngTc6i6H5e
L4x2uxhnWJ
RQVZQxVasQ