Colon-in-Ruby

1. abc: it can’t exist independently
2. :xyz it is a symbol

:xyz.class => Symbol 3) abc::xyz it represents namespace

Example code:

module ABC class Xyz def initialize @size = 400 end end end

x = ABC::Xyz.new 4) abc: :xyz

hash = {abc: :xyz} #hash key and value all are symbol. 5) abc: xyz

xyz = “just a test” hash = {abc: xyz} #hash key is symbol, value is string. 6) :abc => xyz

xyz = “just a test” hash = {:abc => xyz} # same with (5)， just another representation 7) ternary operator :

abc = 1 xyz = 2 result = abc > xyz ? abc : xyz => result = 2

– Copy from http://stackoverflow.com/questions/30315021/colon-placement-in-ruby-on-rails/30315118#30315118