The Book of Ruby

Multiple Iterator Arguments

In the previous chapter, you used a for loop with more than one loop variable to iterate over a multidimensional array. On each turn through the for loop, a variable was assigned one row (that is, one “subarray”) from the outer array:

multi_array.rb

# Here multiarr is an array containing two 'rows'
# (subarrays) at index 0 and 1
multiarr = [    ['one','two','three','four'],
                [1,2,3,4]
           ]
# This for loop runs twice (once for each 'row' of multiarr)
for (a,b,c,d) in multiarr
   print("a=#{a}, b=#{b}, c=#{c}, d=#{d}\n" )
end

The previous loop prints this:

a=one, b=two, c=three, d=four
a=1, b=2, c=3, d=4

However, you could also use the each method to iterate over this four-item array by passing four block parameters—a, b, c, d—into ...