Building Database Applications in Elixir with Ecto/

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Create Schemas

Create Schemas

Learn how to create schemas.

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Let’s look at the DSL Ecto provides to create schemas. We’ll use the DSL to specify the fields we want to map and their data types.

Map schema fields

Let’s start with our tracks table. We’ll have just five fields for now:

  • id, a unique ID for our track.

  • title, a string representing the track’s title.

  • duration, the length of the track in seconds.

  • index, a number representing the track’s position in an album.

  • number_of_plays, a counter that we increment every time we play the track.

If we’re writing an Elixir application that doesn’t use Ecto, we would most likely create a %Track{} struct to hold this data. We need to open a file named track.ex and add something like this:

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defmodule MusicDB.Track do
  defstruct [:id, :title, :duration, :index, :number_of_plays]
end

With Ecto, the process is similar. Rather than defstruct, we’ll use the schema macro, and rather than a list of atoms, we’ll provide fields. With these changes, our code will look like this:

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defmodule MusicDB.Track do 
  use Ecto.Schema
  schema "tracks" do
    field :title, :string
    field :duration, :integer
    field :index, :integer
    field :number_of_plays, :integer 
    timestamps()
   end 
end

What do we do?

This defines a new %Track{} ...