Ruby and Coffeescript destructured assignment

temp.coffee

# more info at http://coffeescript.org/#destructuring

# Coffeescript also allows "pattern matching" style assignment
args =
  column:
    isBand: false
    foo: 'bar'
  row:
    dataRowIndex: 1
    foo: 'bar'
  _cellIndex: 1
  foo: 'bar'

{column: 
  isBand: band
  row: 
    dataRowIndex: rowIndex
  _cellIndex: cellIndex} = args

band #=> false
rowIndex #=> 1
cellIndex #=> 1

temp.rb

def Array.toy(size=10)
  (1..size).to_a
end

arr = Array.toy #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# without a splat, only elements are assigned
head, second, rest = arr #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
head #=> 1
second #=> 2
rest #=> 3

# with a splat, the rest are put in the splatted var
head, second, *rest = arr #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
head #=> 1
second #=> 2
rest #=> [3, 4, 5, 6, 7, 8, 9, 10]

# splat can be on any arg
head, *mid, tail = arr #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
head #=> 1
mid #=> [2, 3, 4, 5, 6, 7, 8, 9]
tail #=> 10

# extra elements get nil
first, second, third = [1,2] #=> [1, 2]
first #=> 1
second #=> 2
third #=> nil

# blocks also allow this (as do method calls)
{:a => [1,2], :b => [3,4]}.each do |k,v|
  puts "k: #{k}"
  puts "v: #{v}"
end #=> {:a=>[1, 2], :b=>[3, 4]}
# prints:
# k: a
# v: [1, 2]
# k: b
# v: [3, 4]

# destructuring value
{:a => [1,2], :b => [3,4]}.each do |k,(a,b)|
  puts "k: #{k}"
  puts "a: #{a}"
  puts "b: #{b}"
end #=> {:a=>[1, 2], :b=>[3, 4]}
# prints:
# k: a
# a: 1
# b: 2
# k: b
# a: 3
# b: 4

# parallel assignment
a = 1 #=> 1
b = 2 #=> 2
a, b = b, a #=> [2, 1]
a #=> 2
b #=> 1