class ActiveAdmin::ResourceCollection

It’s assumed that an added resource responds to ‘resource_name`.
This is a container for resources, which acts much like a Hash.

def [](obj) 

def [](obj)
  @collection[obj] || find_resource(obj)
end

def add(resource) 

def add(resource)
  if match = @collection[resource.resource_name]
    raise_if_mismatched! match, resource
    match
  else
    @collection[resource.resource_name] = resource
  end
end

def each(&block)

Changes `each` to pass in the value, instead of both the key and value. 
def each(&block)
  values.each &block
end

def find_resource(obj)

Finds a resource based on the resource name, resource class, or base class. 
def find_resource(obj)
  resources.detect do |r|
    r.resource_name.to_s == obj.to_s
  end || resources.detect do |r|
    r.resource_class.to_s == obj.to_s
  end ||
  if obj.respond_to? :base_class
    resources.detect{ |r| r.resource_class.to_s == obj.base_class.to_s }
  end
end

def initialize 

def initialize
  @collection = {}
end

def raise_if_mismatched!(existing, given) 

def raise_if_mismatched!(existing, given)
  if existing.class != given.class
    raise IncorrectClass.new existing, given
  elsif given.class <= Resource && existing.resource_class != given.resource_class
    raise ConfigMismatch.new existing, given
  end
end

def resources 

def resources
  select{ |r| r.class <= Resource } # can otherwise be a Page
end