Add comma in array first element in Rails

I have an array in Ruby on Rails.

[city, state, zip].reject(&:blank?).join(' ')

I want to add comma after first element of an array i.e city

"Atlanta, GA 30114"

Rails 6.1 introduced Enumerable#compact_blank. You can use it instead of reject(&:blank?)

If you need add comma only after the city, just add comma to the city if it is present

def format_city(city, state, zip)
  city_with_comma = "#{city}," if city.present?
  [city_with_comma, state, zip].compact_blank.join(" ")
end

format_city(nil, "GA", "30114")
# => "GA 30114"

format_city("Atlanta", "GA", "30114")
# => "Atlanta, GA 30114"

To add a comma after the first element of an array in Ruby on Rails:

result = [array[0], array[1..-1].reject(&:blank?).join(' ')].join(', ')
puts result

reject(&:blank?) Ensures that any blank or empty elements are removed from the resulting array.

join(', ') combines the elements of the array into a string, separated by a comma and space

result variable will hold the desired output: "Atlanta, GA 30114", with a comma after the city name.

Interesting fact:

blank? Is commonly used in Ruby on Rails instead of empty? which is commonly used in default Ruby

lots of ways to do it... here's another...

city,state,zip = ["Atlanta","GA","30114"]
[(city+"," if city),state,zip].compact.join(" ") => "Atlanta, GA 30114"

when city is blank:

city,state,zip = [nil,"GA","30114"]
[(city+"," if city),state,zip].compact.join(" ") => "GA 30114"