Interactor encapsulates your business logic. Interactor is a simple object with an only one goal.

Methodist interactors work using dry-transaction

It's simple. Just create your interactor with:

rails generate interactor hello/world

This command will generate a file #{Rails.root}/app/interactors/hello/world.rb with code:

class Hello::World < Methodist::Interactor
  schema do
    # schema code goes here
  end

  step :validate
end

As you can see in the class body we have #schema method with the pass block. We need it for validation. We have step :validate below, where step is one of a step adapter from dry-transaction and :validate is a validation method. You should read this doc to understand how does the step adapter work. Learn more about validations below.

Now add a validation schema and one more step to our interactor:

class Hello::World < Methodist::Interactor
  schema do
    required(:name).value(:str?)
  end

  step :validate
  step :say_hello

  def say_hello(input)
    puts "Hello, #{input[:name]}"
    Success(input)
  end
end

We define #say_hello but don't define #validate. Why? Because #validate has already defined in a Methodist::Interactor class. You can redefine it after your steps.

Now you can use our first interactor:

Hello::World.new.call(name: 'QNester')
#> Hello, QNester
#> Success({ name: 'QNester' })

You can check the interactor execution result:

result = Hello::World.new.call(name: 'QNester')
result.success? #> true
result.value #> { name: 'QNester' }

Learn more about dry-transaction behavior here: http://dry-rb.org/gems/dry-transaction/basic-usage/

Methodist interactors have a built-in validation mechanism by dry-validation

To use built in #validate method in your interactors, pass your validations to the #shema method.

Example:

# app/interactors/hello/world.rb
class Hello::World < Methodist::Interactor
  schema do
    required(:name).value(:str?)
  end

  step :validate
  step :say_hello

  def say_hello(input)
    puts "Hello, #{input[:name]}"
    Success(input)
  end
end

# success
result = Hello::World.new.call(name: 'QNester')
result.success? #> true

# failure
another_result = Hello::world.new.call
another_result.success? #> false
another_result.value #> { error: 'ValidationError', field: :name, reason: 'name: must exists' }

If you want to customize the value returned in case of validation failure, redefine a #failure_validation_value method.

To create your own validation method, use one of these approaches:

1. redefine a #validate method;
2. define #your_custom_method and use it like that step :your_custom_method instead of step :validate.

About dry-validation schemas here.