Massager

Have you ever felt a need to massage your data just a little bit before working with it? This is what Massager was built for.

Installation

Add this line to your application's Gemfile:

gem 'massager'

And then execute:

$ bundle

Or install it yourself as:

$ gem install massager

Simplest usecase

To start using Massager, just include it in your classes, like so:

class ExampleClass
  include Massager
  attribute :foo, "bar"
end

In this scenario, the "bar" key's value will become the result foo method

testable = ExampleClass.call({"bar" => "value"})
testable.foo #=> "value"

Strict schema

You can have required keys defined with strict: true

class ExampleClass
  include Massager
  attribute :foo, "bar", strict: true
end

It will raise an error if "bar" is not passed:

testable = ExampleClass.call({"bar" => "value"})
testable.foo #=> "value"
testable = ExampleClass.call({"baz" => "value"}) #=> raises ArgumentError

Type checking

You can also pass type checks using dry-types library:

class ExampleClass
  include Massager
  attribute :foo, "bar", type: Types::Strict::String
end

It will raise an error if the type is not correct:

testable = ExampleClass.call({"bar" => "value"})
testable.foo #=> "value"
testable = ExampleClass.call({"bar" => 123})  #=> raises Dry::Types::ConstraintError

If you want to define your own types, check the Dry Types library. Type needs to respond to call method, so you can define your own

Preprocessing the value via block

You can add bit of preprocessing via block (The type check will be preformed afer the block is executed):

class ExampleClass
  include Massager
  attribute :foo, "bar", type: Types::Strict::String do |v|
    v.upcase
  end
end

And it will have following result

testable = ExampleClass.call({"bar" => "value"})
testable.foo #=> "VALUE"

Combining multiple keys

class ExampleClass
  include Massager
  attribute :foo, "bar", "baz", type: Types::Strict::String do |bar, baz|
    "#{bar} #{baz}"
  end
end

Note that if you pass multiple keys, the modifier block is mandatory

testable = ExampleClass.call({"bar" => "bar", "baz" => "baz"})
testable.foo #=> "bar baz"

License

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