Discriminate first and last element in each?

Question

@example.each do |e|
  #do something here
end

Here I want to do something different with the first and last element in each, how should I achieve this?

Answer 1

You can use each_with_index and then use the index to identify the first and last items. For example:

@data.each_with_index do |item, index|
  if index == 0
    # this is the first item
  elsif index == @data.size - 1
    # this is the last item
  else
    # all other items
  end
end

Alternately, if you prefer you could separate the 'middle' of the array like so:

# This is the first item
do_something(@data.first)

@data[1..-2].each do |item|
  # These are the middle items
  do_something_else(item)
end

# This is the last item
do_something(@data.last)

With both these methods you have to be careful about the desired behaviour when there are only one or two items in the list.