Shale::Builder

This addon to the shale Ruby gem adds a simple yet powerful builder DSL.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add shale-builder

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install shale-builder

Usage

TLDR

Build your shale classes like a boss.

transaction = Transaction.build do |t|
    t.cvv_code = '123'
    t.amount do |a|
        a.value = 2.3
        a.currency = 'PLN'
    end
    t.payment_instrument do |p|
        p.number = '4242424242424242'
        p.expiration_year = 2045
        p.expiration_month = 12
    end
end

Build method

This gem adds a module named Shale::Builder. It's meant to be included in subclasses of Shale::Mapper to provide an easier way of building instances.

You can use it like that:

require 'shale/builder'

class Amount < Shale::Mapper
    include Shale::Builder

    attribute :value, Shale::Type::Float
    attribute :currency, Shale::Type::String
end

Now instead of creating an instance like that:

amount = Amount.new(value: 2.3, currency: 'PLN')

You can do it like that:

amount = Amount.build do |a|
    a.value = 2.3
    a.currency = 'PLN'
end

Building nested objects

It's kind of pointless when you've got a flat structure. It really shines when nested objects come into play.

Let's say that you've got a structure like this:

class Amount < Shale::Mapper
    include Shale::Builder

    attribute :value, Shale::Type::Float
    attribute :currency, Shale::Type::String
end

class PaymentInstrument < Shale::Mapper
    include Shale::Builder

    attribute :number, Shale::Type::String
    attribute :expiration_year, ::Shale::Type::Integer
    attribute :expiration_month, ::Shale::Type::Integer
end

class Transaction < Shale::Mapper
    include Shale::Builder

    attribute :cvv_code, Shale::Type::String
    attribute :amount, Amount
    attribute :payment_instrument, PaymentInstrument
end

Normally you would instantiate it like that:

transaction = Transaction.new(
    cvv_code: '123',
    amount: Amount.new(
        value: 2.3,
        currency: 'PLN'
    ),
    payment_instrument: PaymentInstrument.new(
        number: '4242424242424242',
        expiration_year: 2045,
        expiration_month: 12
    )
)

It's really repetitive and it makes it hard to modify the values of certain attributes or omit them conditionally.

This gem provides a better way:

transaction = Transaction.build do |t|
    t.cvv_code = '123'
    t.amount do |a|
        a.value = 2.3
        a.currency = 'PLN'
    end
    t.payment_instrument do |p|
        p.number = '4242424242424242'
        p.expiration_year = 2045
        p.expiration_month = 12
    end
end

That's possible because the getters of attributes with non-primitive types have been overridden to accept blocks. When a block is given to such a getter, it instantiates an empty object of its type and yields it to the block.

Collections

Whenever you call a getter with a block for a collection attribute, the built object will be appended to the array.

Let's define a schema like this.

class Client < Shale::Mapper
    include Shale::Builder

    attribute :first_name, Shale::Type::String
    attribute :last_name, Shale::Type::String
    attribute :email, Shale::Type::String
end

class Transaction < Shale::Mapper
    include Shale::Builder

    attribute :clients, Client, collection: true
end

You can easily build add new clients to the collection like so:

transaction = Transaction.build do |t|
  # this will be added as the first element of the collection
  t.clients do |c|
    c.first_name = 'Foo'
    c.last_name = 'Bar'
  end

  # this will be added as the second element of the collection
  t.clients do |c|
    c.first_name = 'Grant'
    c.last_name = 'Taylor'
  end
end

p transaction.clients
# [
#    #<Client:0x00000001066c2828 @first_name="Foo", @last_name="Bar", @email=nil>,
#    #<Client:0x00000001066c24b8 @first_name="Grant", @last_name="Taylor", @email=nil>
# ]

Conditional building

This DSL makes it extremely easy to build nested objects conditionally.

transaction = Transaction.build do |t|
    t.cvv_code = '123'
    t.amount do |a|
        a.value = 2.3 if some_flag?
        a.currency = 'PLN'
    end
    t.payment_instrument do |p|
        p.number = '4242424242424242'
        if some_condition?
            p.expiration_year = 2045
            p.expiration_month = 12
        end
    end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Verseth/ruby-shale-builder.

License

The gem is available as open source under the terms of the MIT License.

shale-builder

Runtime