I've got the following array:
a = ['sda', 'sdb', 'sdc', 'sdd']
Now I want to loop through these entries but always with two elements. I do this like the following at the moment:
while b = a.shift(2)
# b is now ['sda', 'sdb'] or ['sdc', 'sdd']
end
This feels somehow wrong, is there a better way to do this? Is there a way to get easily to something like [['sda', 'sdb'], ['sdc', 'sdd']] ?
I read http://www.ruby-doc.org/core-1.9.3/Array.html but I didn't find something useful...
You might want to look at Enumerable instead, which is included in Array.
The method you want is Enumerable#each_slice, which repeatedly yields from the enumerable the number of elements given (or less if there aren't that many at the end):
a = ['sda', 'sdb', 'sdc', 'sdd']
a.each_slice(2) do |b|
p b
end
Yields:
$ ruby slices.rb
["sda", "sdb"]
["sdc", "sdd"]
$
Enumerator actually includes Enumerable as well; you could think of Enumerator like a generic interface to do enumerating things; if you call [1, 2, 3].each or ['sda', 'sdb', 'sdc', 'sdd'].each_slice(2)—both without a block—you'll get an Enumerator instance, which you can then further do things to.
['sda', 'sdb', 'sdc', 'sdd'].each_slice(2).to_aIf you need to work with strict pairs you might want to use Enumerable#each_cons method. Here is the difference between each_slice and each_cons:
a = ['a', 'b', 'c', 'd', 'e']
a.each_slice(2) { |i| p i }
# ["a", "b"]
# ["c", "d"]
# ["e"]
a.each_cons(2) { |i| p i }
# ["a", "b"]
# ["b", "c"]
# ["c", "d"]
# ["d", "e"]
