Class: Dry::Transaction::Extra::Steps::Merge

Inherits:
Object
  • Object
show all
Defined in:
lib/dry/transaction/extra/steps/merge.rb

Overview

If you’re using keyword args as the arguments to your steps, you often want a step to add its output to those args, while keeping the original kwargs intact.

* If the output of the step is a Hash, then that hash is merged into the input.
* If the output of the step is not a Hash, then a key is inferred
  from the step name. The name of the key can be overridden with the
  `as:` option.

Examples:

Merging Hash output


merge :add_context

# Input: { user: #<User id:42>, account: #<Account id:1> }
def add_context(user:, **)
  {
    email: user.email,
    token: UserToken.lookup(user)
  }
end
# Output: { user: #<User id:42>,
            account: #<Account id:1>,
            email: "[email protected]",
            token: "1234" }

Merging non-Hash output, inferring the key from the step name


merge :user

# Input: { id: 42 }
def user(id:, **)
  User.find(id)
end
# Output: { id: 42, user: #<User id:42> }

Merging non-Hash output, specifying the key explicitly


merge :find_user, as: :current_user

# Input: { id: 42 }
def find_user(id:, **)
  User.find(id)
end
# Output: { id: 42, current_user: #<User id:42> }

Instance Method Summary collapse

Instance Method Details

#call(operation, options, args) ⇒ Object 



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# File 'lib/dry/transaction/extra/steps/merge.rb', line 57

def call(operation, options, args)
  if args.size > 1 || (!args[0].is_a?(Hash) && !args[0].nil?)
    raise ArgumentError,
          "the merge step only works with keyword arguments"
  end

  result = operation.call(*args)
  return result if result.is_a?(Failure)

  value = result.is_a?(Success) ? result.value! : result
  unless value.is_a?(Hash)
    key = options[:as] || options[:step_name]
    value = { key.to_sym => value }
  end

  Success((args[0] || {}).merge(value))
end