View Source Commanded.Projections.Ecto behaviour (commanded_ecto_projections v1.3.0)
Read model projections for Commanded using Ecto.
example-usage
Example usage
defmodule Projector do
use Commanded.Projections.Ecto,
application: MyApp.Application,
name: "my-projection",
repo: MyApp.Repo,
schema_prefix: "my-prefix",
timeout: :infinity
project %Event{}, _metadata, fn multi ->
Ecto.Multi.insert(multi, :my_projection, %MyProjection{...})
end
project %AnotherEvent{}, fn multi ->
Ecto.Multi.insert(multi, :my_projection, %MyProjection{...})
end
end
guides
Guides
Link to this section Summary
Callbacks
The optional after_update/3 callback function defined in a projector is
called after each projected event.
The optional schema_prefix/1 callback function defined in a projector is
used to set the schema of the projection_versions table used by the
projector for idempotency checks.
The optional schema_prefix/2 callback function defined in a projector is
used to set the schema of the projection_versions table used by the
projector for idempotency checks.
Functions
Project a domain event into a read model by appending one or more operations
to the Ecto.Multi struct passed to the projection function you define
Project a domain event and its metadata map into a read model by appending one
or more operations to the Ecto.Multi struct passed to the projection
function you define.
Link to this section Callbacks
@callback after_update( event :: struct(), metadata :: map(), changes :: Ecto.Multi.changes() ) :: :ok | {:error, any()}
The optional after_update/3 callback function defined in a projector is
called after each projected event.
The function receives the event, its metadata, and all changes from the
Ecto.Multi struct that were executed within the database transaction.
You could use this function to notify subscribers that the read model has been updated, such as by publishing changes via Phoenix PubSub channels.
example
Example
defmodule MyApp.ExampleProjector do
use Commanded.Projections.Ecto,
application: MyApp.Application,
repo: MyApp.Projections.Repo,
name: "MyApp.ExampleProjector"
project %AnEvent{name: name}, fn multi ->
Ecto.Multi.insert(multi, :example_projection, %ExampleProjection{name: name})
end
@impl Commanded.Projections.Ecto
def after_update(event, metadata, changes) do
# Use the event, metadata, or `Ecto.Multi` changes and return `:ok`
:ok
end
endThe optional schema_prefix/1 callback function defined in a projector is
used to set the schema of the projection_versions table used by the
projector for idempotency checks.
It is passed the event and its metadata and must return the schema name, as a
string, or nil.
The optional schema_prefix/2 callback function defined in a projector is
used to set the schema of the projection_versions table used by the
projector for idempotency checks.
It is passed the event and its metadata, and must return the schema name, as a
string, or nil
Link to this section Functions
Project a domain event into a read model by appending one or more operations
to the Ecto.Multi struct passed to the projection function you define
The operations will be executed in a database transaction including an idempotency check to guarantee an event cannot be projected more than once.
example
Example
project %AnEvent{}, fn multi ->
Ecto.Multi.insert(multi, :my_projection, %MyProjection{...})
endProject a domain event and its metadata map into a read model by appending one
or more operations to the Ecto.Multi struct passed to the projection
function you define.
The operations will be executed in a database transaction including an idempotency check to guarantee an event cannot be projected more than once.
example
Example
project %AnEvent{}, metadata, fn multi ->
Ecto.Multi.insert(multi, :my_projection, %MyProjection{...})
end