Easier (un)nesting

[risen]

Hi,

I'm evaluating shale for a project, and was wondering if there's an easier way to get from flattened JSON to nested models.

Example:

class Person < ApplicationRecord
  belongs_to :address

  # attribute :id
  # attribute :name
end

class Address < ApplicationRecord
  # attribute :street
  # attribute :city
end

class PersonMapper < Shale::Mapper
  model Person

  attribute :id,     Shale::Type::Integer
  attribute :name,   Shale::Type::String
  attribute :street, Shale::Type::String
  attribute :city,   Shale::Type::String

  json do
    map :street, to: { address: :street }
    map :city,   to: { address: :city }
  end

  def address_from_json(model, key, value)
    model.build_address unless model.address
  end
end

… something like this. I could create a method for every single attribute that's "delegated" to address, but it gets verbose and tedious.

• The "to: with hash" api is just an example, there's probably a better way
• Could there also be a way to initialize the nested relation properly (model.build_address)
• Is there an existing way that I overlooked?

[kgiszczak]

Hey, currently there's no other way to do it - you have to use method for every attribute.

I wonder if something like this could solve most of this kind of use cases:

class PersonMapper < Shale::Mapper
  model Person

  attribute :id,     Shale::Type::Integer
  attribute :name,   Shale::Type::String

  json do
    map ['street', 'city'], using: { from: :address_from_json }
  end

  # hash would be { 'street' => 'foo', 'city' => 'bar' }
  def address_from_json(model, hash)
    model.build_address(hash)
  end
end

I'll have to think about all the use cases that can be solved by this. I don't want to add something that's coupled with a single, domain specific use case.

[kgiszczak]

I just released a new version that allows you to map group of elements using methods e.g.

class Person < Shale::Mapper
  attribute :name, Shale::Type::String

  json do
    group from: :name_from_json, to: :name_to_json do
      map 'first_name'
      map 'last_name'
    end
  end

  def name_from_json(model, value)
    model.name = "#{value['first_name']} #{value['last_name']}"
  end

  def name_to_json(model, doc)
    doc['first_name'] = model.name.split(' ')[0]
    doc['last_name'] = model.name.split(' ')[1]
  end
end

person = Person.from_json(<<~DATA)
{
  "first_name": "John",
  "last_name": "Doe"
}
DATA

Release notes are here: https://www.shalerb.org/releases.html#v080

I'm closing the issue, if you have more questions feel free to create a new one. Thanks.