How to sort collection by created_at attribute

Question

I'm working with Ruby on Rails 2.3.8 and I've got a collection that is built from other two collections, as follows:

@coll1 = Model1.all
@coll2 = Model2.all

@coll = @coll1 << @coll2

Now, I would like to sort that collection by created_at attribute in descendant order. So, I did the following:

@sorted_coll = @coll.sort {|a,b| b.created_at <=> a.created_at}

And I've got the following exception:

undefined method `created_at' for #<Array:0x5c1d440>

eventhought it exists for those models.

Could anyboy help me please?

Answer 1

You were pushing another array as another element into the @coll1 array, you have two options:

Flatten the resulting array:

@coll.flatten!

Or preferably just use the + method:

@coll = @coll1 + @coll2

And for sorting you should use sort_by:

@sorted_coll = @coll.sort_by { |obj| obj.created_at }

Answer 2

@coll1 = Model1.all
@coll2 = Model2.all

@coll = @coll1 + @coll2

@sorted_coll = @coll.sort_by { |a| a.created_at }