This allows you to take multiple Operation objects and encapsulate them to form a single object, which can then be used to send a single request to AWS. This allows for greater efficiency, reducing the number of requests sent to AWS.

AWS currently imposes a limit of two operations when encapsulating operations in a multiple operation. Note, however, that one or both of these operations may be a batched operation. Combining two batched operations in this way makes it possible to send as many as four simple operations to AWS in a single MultipleOperation request.

operations is an array of objects subclassed from Operation, such as ItemSearch, ItemLookup, etc.

Please note the following implementation details:

• As mentioned above, Amazon currently imposes a limit of two operations encapsulated in a MultipleOperation.
• To use a different set of response groups for each encapsulated operation, assign to each operation‘s @response_group attribute prior to encapulation in a MultipleOperation.
• To use the same set of response groups for all encapsulated operations, you can directly assign to the @response_group attribute of the MultipleOperation. This will propagate to the encapsulated operations.
• One or both operations may have multiple results pages available, but only the first page will be returned by your requests. If you need subsequent pages, you must perform the operations separately. It is not possible to page through the results of a MultipleOperation response.
• In this implementation, an error in any of the constituent operations will cause an exception to be thrown. If you don‘t want partial success (i.e. the success of fewer than all of the operations) to be treated as failure, you should perform the operations separately.
• MultipleOperation is intended for encapsulation of objects from different classes, e.g. an ItemSearch and an ItemLookup. If you just want to batch operations of the same class, Operation#batch provides an alternative.

  In fact, if you create a MultipleOperation encapsulating objects of the same class, Ruby/AWS will actually apply simple batch syntax to your request, so it amounts to the same as using Operation#batch.

• Although all of the encapsulated operations can be batched operations, Amazon places a limit of two on the number of same-class operations that can be carried out in any one request. This means that you cannot encapsulate two batched requests from the same class, so attempting, for example, four ItemLookup operations via two batched ItemLookup operations will not work.

Example:

 is = ItemSearch.new( 'Books', { 'Title' => 'Ruby' } )
 il = ItemLookup.new( 'ASIN', { 'ItemId' => 'B0013DZAYO',
                                'MerchantId' => 'Amazon' } )
 is.response_group = ResponseGroup.new( :Large )
 il.response_group = ResponseGroup.new( :Small )
 mo = MultipleOperation.new( is, il )

[Source]

# File lib/amazon/aws.rb, line 814
      def initialize(*operations)

        # Start with an empty parameter hash.
        #
        super( {} )
        
        # Start off with the first operation and duplicate the original's
        # parameters to avoid accidental in-place modification.
        #
        operations.flatten!
        @params = operations.shift.params.freeze.dup

        # Add subsequent operations' parameter hashes, protecting them
        # against accidental in-place modification.
        #
        operations.each do |op|
          op.params.freeze.each do |op_kind, op_arr|
            @params[op_kind].concat( op_arr )
          end
        end

      end