Concise way of passing an argument to a method when the argument is not nil

optional.rb

# One line: dead simple.
o = ->(arg) { arg.nil? ? [] : [arg] }

# Usage example:
def some_method(required_arg, optional_arg=:default)
  puts "Got required_arg: #{required_arg.inspect}"
  puts "Got optional_arg: #{optional_arg.inspect}"
end

pass_this = "Required arg"
maybe_pass_this = nil

# This passes nil explicitly, which we don't want
some_method(pass_this, maybe_pass_this)

# This method is nice, but is sort of bulky
some_method(pass_this, *[maybe_pass_this].compact)

# Pretty and concise
some_method(pass_this, *o[maybe_pass_this])

# If you don't like the name `o`, there are alternatives:
opt = o
some_method(pass_this, *opt[maybe_pass_this])

optional = o
some_method(pass_this, *optional[maybe_pass_this])

# Or you can use parens instead of brackets:
define_singleton_method(:o, &o)
some_method(pass_this, *o(maybe_pass_this))