05_Formats.md

Stream formats in action

Since we have already discussed what stream formats are and how to use them, let's make use of them in our project! The first thing to do is to define modules responsible for describing the formats used in our pipeline. We will put them in a separate directory - lib/formats. Let's start with the format describing the packets:

lib/formats/packet_format.ex

defmodule Basic.Formats.Packet do
 @moduledoc """
 A module describing the format of the packet.
 """
 defstruct type: :custom_packets
end

The definition of the module is not complicated, as you can see in the code snippet above - we are only defining a structure within that module, with a :type parameter, whose default value is :custom_packets.

In our pipeline we will also send another type of data - frames. Let's define a format for them:

lib/formats/frame_format.ex

defmodule Basic.Formats.Frame do
 @moduledoc """
 A module describing the format of the frame.
 """
 defstruct encoding: :utf8
end

Same as in the case of the previous format - we are defining a structure with a single field, called :encoding, and the default value of that field - :utf8.

That's it! Format modules are really simple, and using them is not that hard either, as you will see in the subsequent chapters - defining the accepted stream formats and sending stream format actions!

Before advancing you can test the Source element, using the tests provided in /test directory.

mix test test/elements/source_test.exs

In case of errors, you may go back to the Source chapter or take a look how Source and formats should look like.