Add in_groups to ActiveSupport::CoreExtensions::Array::Grouping

Pratik,

I would gladly continue the discussion in the Rails Core mailing list. Still, let me comment on complexity and use cases.

The method interface matches 1:1 the one for in_groups_of -- which in the scope of Rails, lays on the easy side. So use shouldn't be a problem to anyone already using in_groups_of.

Both methods appear as a natural fit. When slicing an array you're usually concerned about either: subarray size (where you would use in_groups_of) or, number of subarrays (where you could use in_groups).

Possible use cases are: view code for n-column layout as in "x accounts/addresses to be splitted in y elements to be floated and rendered as columns"; resource allocation as in "x conference attendees to be arranged along y available rooms"; and many others.

Fixed a bug in test_in_groups_returned_array_size.

I found the example code in the ticket a little confusing and didn't see the point. Then it clicked in my head that where the existing method says "divide this into n groups of three" this says "divide this into three groups of n". You can see this a little better in:

1. Produces four groups of three

>> %w(1 2 3 4 5 6 7 8 9 10).in_groups_of(3)

=> [["1", "2", "3"], ["4", "5", "6"], ["7", "8", "9"], ["10", nil, nil]]

1. Produces three groups of four

%w(1 2 3 4 5 6 7 8 9 10).in_groups(3)

=> [["1", "2", "3", "4"], ["5", "6", "7", nil], ["8", "9", "10", nil]]

It seems like a natural converse method to me. :)

Those numbers were supposed to be comments using #. Silly me forgot about formatting.

RSL, thanks for coming up with much better wording and code samples! :-)

Looks useful, +1

Though I'd like to point out that if anyone should need a columns-first order (which gives the same fill as in_groups, but the elements are first ordered by row and then column), there are two ways:

1. Here 4 is the number of result groups

>> %w(1 2 3 4 5 6 7 8 9 10).in_groups_of(4).transpose

=> [["1", "5", "9"], ["2", "6", "10"], ["3", "7", nil], ["4", "8", nil]]

1. Or another way to do the same:

>> y=%w(1 2 3 4 5 6 7 8 9 10).in_groups_of(4)

=> [["1", "2", "3", "4"], ["5", "6", "7", "8"], ["9", "10", nil, nil]]

>> y.shift.zip(*y)

=> [["1", "5", "9"], ["2", "6", "10"], ["3", "7", nil], ["4", "8", nil]]

Summarized both commits as one.