Activity-DSL-Linear

The trailblazer-activity-dsl-linear gem brings the popular step DSL around the activity gem. It allows to create classes that you might mostly know as operations - service objects that execute your business logic in a certain order, depending on how you harness the step DSL.

Please find the full documentation on the Trailblazer website.

Example

The activity-dsl-linear gem provides three default patterns to model activities: Path, Railway and FastTrack. Here's an example of what a railway activity could look like, along with some more complex connections (you can read more about Railway strategy in the docs).

require "trailblazer-activity-dsl-linear"

class Memo::Update < Trailblazer::Activity::Railway
  # Use the DSL to describe the layout of the activity.
  step :find_model
  step :validate, Output(:failure) => End(:validation_error)
  step :save
  fail :log_error

  # Here comes your business logic.
  def find_model(ctx, id:, **)
    ctx[:model] = Memo.find_by(id: id)
  end

  def validate(ctx, params:, **)
    return true if params[:body].is_a?(String) && params[:body].size > 10
    ctx[:errors] = "body not long enough"
    false
  end

  def save(ctx, model:, params:, **)
    model.update_attributes(params)
  end

  def log_error(ctx, params:, **)
    ctx[:log] = "Some idiot wrote #{params.inspect}"
  end
end

Visually, this would translate to the following circuit.

You can run the activity by invoking its call method.

ctx = { id: 1, params: { body: "Awesome!" } }

signal, (ctx, *) = Update.( [ctx, {}] )

pp ctx #=>
{:id=>1,
 :params=>{:body=>"Awesome!"},
 :model=>#<Memo body=nil>,
 :errors=>"body not long enough"}

pp signal #=> #<struct Trailblazer::Activity::End semantic=:validation_error>

With Activity, modeling business processes turns out to be ridiculously simple: You define what should happen and when, and Trailblazer makes sure that it happens.

Features

Activities can model any process with arbitrary flow and connections.
Nesting and compositions are allowed and encouraged (via Trailblazer's dsl-linear gem).
Different step interfaces, manual processing of DSL options, etc is all possible.
Steps can be any kind of callable objects.
Tracing! (via Trailblazer's developer gem)

Operation

Trailblazer's Operation internally uses an activity to model the processes.

Workflow

Activities can be formed into bigger compounds and using workflow, you can build long-running processes such as a moderated blog post or a parcel delivery. Also, you don't have to use the DSL but can use the editorinstead(cool for more complex, long-running flows). Here comes a sample screenshot.

License

Licensed under the LGPLv3 license. We also offer a commercial-friendly license.