Finding the previous / next item

Rails
#1

Given one model with a more complex sort in it.
@products = Product.all

If I now have the ID of a product that is in @products - what is the
best
way to find the previous/next element (keeping the model sort in mind,
e.g.
the previous / next with respect to the custom sort, not with respect to
the
database)? Is there a better way than stepping through using .each?

#2

On Wed, Jan 5, 2011 at 5:28 AM, bourne [email protected] wrote:

Given one model with a more complex sort in it.
@products = Product.all

If I now have the ID of a product that is in @products - what is the best
way to find the previous/next element (keeping the model sort in mind, e.g.
the previous / next with respect to the custom sort, not with respect to the
database)? Is there a better way than stepping through using .each?

@products is just an Array; you should look through the doc to see
the methods available. You might find Array#index and Array#at of
interest. :slight_smile:

HTH,

Hassan S. ------------------------ [email protected]
twitter: @hassan

#3

Hassan S. wrote in post #972525:

@products is just an Array; you should look through the doc to see
the methods available. You might find Array#index and Array#at of
interest. :slight_smile:

In other words. A Ruby Array (@products.class => Array) is an ordered
list, as opposed to Hash or Set, which store unordered collections of
objects.

So if you order the records from a fetch such as:

@products = Product.order(:name)

The Array will maintain the objects in the order specified in the query.
And getting next or previous is just as Hassan explained:

product = @products.at(3)
next_product = product.index(@products.index(product) +1)

Note. Don’t forget to check the array bounds or you might get unexpected
results.

#4

Thanks for the pointer to .at.

For the archives:

    @product_before = 'tablehead'
    @productindex = @products.index(@product)
    if @productindex
      if @productindex > 0
        @product_before = 'product_' + @products.at(@productindex -

1).id.to_s
end
end