model.rb in wcc-contentful-0.2.0

- old
+ new
@@ -3,22 +3,103 @@
 
 class WCC::Contentful::Model
   extend WCC::Contentful::Helpers
   extend WCC::Contentful::ModelValidators
 
+  # The Model base class maintains a registry which is best expressed as a
+  # class var.
+  # rubocop:disable Style/ClassVars
+
   class << self
+    ##
+    # The configured store which executes all model queries against either the
+    # Contentful CDN or a locally-downloaded copy.
+    #
+    # See the {sync_store}[rdoc-ref:WCC::Contentful::Configuration.sync_store] parameter
+    # on the WCC::Contentful::Configuration class.
     attr_accessor :store
+
+    def const_missing(name)
+      raise WCC::Contentful::ContentTypeNotFoundError,
+        "Content type '#{content_type_from_constant(name)}' does not exist in the space"
+    end
   end
 
+  @@registry = {}
+
   def self.all_models
+    # TODO: this needs to use the registry but it's OK for now cause we only
+    # use it in specs
     WCC::Contentful::Model.constants(false).map { |k| WCC::Contentful::Model.const_get(k) }
   end
 
+  ##
+  # Finds an Entry or Asset by ID in the configured contentful space
+  # and returns an initialized instance of the appropriate model type.
+  #
+  # Makes use of the configured {store}[rdoc-ref:WCC::Contentful::Model.store]
+  # to access the Contentful CDN.
   def self.find(id, context = nil)
     return unless raw = store.find(id)
 
     content_type = content_type_from_raw(raw)
 
-    const = WCC::Contentful::Model.const_get(constant_from_content_type(content_type))
+    unless const = @@registry[content_type]
+      begin
+        # The app may have defined a model and we haven't loaded it yet
+        const = Object.const_missing(constant_from_content_type(content_type).to_s)
+      rescue NameError
+        nil
+      end
+    end
+    unless const
+      # Autoloading couldn't find their model - we'll register our own.
+      const = WCC::Contentful::Model.const_get(constant_from_content_type(content_type))
+      register_for_content_type(content_type, klass: const)
+    end
+
     const.new(raw, context)
   end
+
+  ##
+  # Registers a class constant to be instantiated when resolving an instance
+  # of the given content type.  This automatically happens for the first subclass
+  # of a generated model type, example:
+  #
+  #   class MyMenu < WCC::Contentful::Model::Menu
+  #   end
+  #
+  # In the above case, instances of MyMenu will be instantiated whenever a 'menu'
+  # content type is resolved.
+  # The mapping can be made explicit with the optional parameters.  Example:
+  #
+  #   class MyFoo < WCC::Contentful::Model::Foo
+  #     register_for_content_type 'bar' # MyFoo is assumed
+  #   end
+  #
+  #   # in initializers/wcc_contentful.rb
+  #   WCC::Contentful::Model.register_for_content_type('bar', klass: MyFoo)
+  def self.register_for_content_type(content_type = nil, klass: nil)
+    klass ||= self
+    raise ArgumentError, "#{klass} must be a class constant!" unless klass.respond_to?(:new)
+    content_type ||= content_type_from_constant(klass)
+
+    @@registry[content_type] = klass
+  end
+
+  ##
+  # Returns the current registry of content type names to constants.
+  def self.registry
+    return {} unless @@registry
+    @@registry.dup.freeze
+  end
+
+  ##
+  # Checks if a content type has already been registered to a class and returns
+  # that class.  If nil, the generated WCC::Contentful::Model::{content_type} class
+  # will be resolved for this content type.
+  def self.registered?(content_type)
+    @@registry[content_type]
+  end
 end
+
+# rubocop:enable Style/ClassVars