Method: Humidifier::Config#map

Defined in:

lib/humidifier/config.rb

#map(type, opts = {}, &block) ⇒ Object

#map is a declaration of a link between a file name and a mapper configuration. It is used to declare the manner in which a set of attributes read from a resource file is converted into instantiations of that type.

For more information about the mapping DSL and how attributes get converted into props, see the Humidifier::Config::Mapper class.

== Basic mapping

For the most basic of mappings, you can just map a file name to a resource, which effectively means that each attribute you provide must map directly to an AWS attribute for that resource, and that no additional attributes will be provided. For example, the following code indicates that files named routes.yml will contain AWS::EC2::Route resources, and that every attribute read will directly correspond to one from AWS:

Humidifier.configure do |config|
  config.map :routes, to: 'EC2::Route'
end

== Using the DSL

For mappings for which you want to use the Humidifier::Config::Mapper DSL, you can pass a block which will get used to create a new mapper class. This is useful for shorter mapper declarations. For example, in the following code we map files named instance_profiles.yml to AWS::IAM::InstanceProfile resources. In that mapping we default the path prop to "/" and we allow the roles prop to just pass a list of roles as an array, which we then convert into CloudFormation references.

Humidifier.configure do |config|
  config.map :instance_profiles, to: 'IAM::InstanceProfile' do
    defaults do |_|
      { path: '/' }
    end

    attribute :roles do |names|
      { roles: names.map { |name| Humidifier.ref(name) } }
    end
  end
end

== Reusing mappers

Finally, if you want to pull the mapper out for reuse, testing, or just separation of code, you can pass the :using key with a mapper as a value. This will cause the given file type to be mapped using whatever class you provided. For example, the following code creates a mapper that automatically tags the resource with the logical name from the stack. It then configures network ACLs to use that so that all network ACL resource declarations automatically have a tag on them with their name.

class NameToTag < Humidifier::Config::Mapper
  defaults do |logical_name|
    { tags: [{ key: 'Name', value: logical_name }] }
  end
end

Humidifier.configure do |config|
  config.map :network_acls, to: 'EC2::NetworkAcl', using: NameToTag
end

# File 'lib/humidifier/config.rb', line 99

def map(type, opts = {}, &block)
  mappings[type.to_sym] = Mapping.new(opts, &block)
end