saturnflyer/casting

Delegate methods in Ruby and preserve self. Add behaviors to your objects without altering their superclass hierarchy.

casting's Issues

Possibly incompatible with New Relic agent (or the other way around.)

We recently integrated New Relic into our application to test out some metrics and it initially connects but starts throwing errors to which Casting is a big part of the stack trace.

I wanted to get some thoughts on this to find out if anyone else is using New Relic and whether or not this has been an issue.

RuntimeError: can't modify frozen NewRelic::Agent::Configuration::ServerSource

/var/bundle/ruby/2.2.0/gems/casting-0.7.1/lib/casting/missing_method_client.rb:50:in `__delegates__'
/var/bundle/ruby/2.2.0/gems/casting-0.7.1/lib/casting/missing_method_client.rb:67:in `method_delegate'
/var/bundle/ruby/2.2.0/gems/casting-0.7.1/lib/casting/missing_method_client.rb:63:in `respond_to_missing?'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/configuration/manager.rb:99:in `respond_to?'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/configuration/manager.rb:99:in `block in source'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/configuration/manager.rb:98:in `each'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/configuration/manager.rb:98:in `source'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction_sample_builder.rb:120:in `transaction_trace_threshold'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction_sample_builder.rb:111:in `finish_trace'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction_sampler.rb:104:in `on_finishing_transaction'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction.rb:519:in `commit!'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction.rb:503:in `stop'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/transaction.rb:148:in `stop'
/var/bundle/ruby/2.2.0/gems/newrelic_rpm-3.16.0.318/lib/new_relic/agent/instrumentation/middleware_tracing.rb:108:in `call'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/configuration.rb:79:in `call'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/server.rb:541:in `handle_request'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/server.rb:388:in `process_client'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/server.rb:270:in `block in run'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/thread_pool.rb:106:in `call'
/var/bundle/ruby/2.2.0/gems/puma-2.15.3/lib/puma/thread_pool.rb:106:in `block in spawn_thread'

The lines in new_relic come down to this

def source(key)
  config_stack.each do |config|
    if config.respond_to?(key.to_sym) || config.has_key?(key.to_sym)
      return config
    end
  end
end

and on the config.respond_to? method which seems to get into the fact that it's trying to initialize @delegates on a frozen object.

Mixin naming: Casting::Client vs. Castable

Tiny detail...

To be consistent with the rest of Ruby's mixins (Enumerable, Comparable, etc.), wouldn't Casting::Client be better named Castable?

Report methods from delegates when querying a client

Currently, an object will respond to messages from its delegates, but if you ask for a collection of methods it will not include those from the delegate.

Casting::MissingMethodClient should report these methods.

methods added by module not accessible from within module

# data object
class Request
  def scheduled_time_from
    'time from'
  end

  def scheduled_time_to
    'time to'
  end
end

# presenter
module RequestPresenter
  def scheduled_time_from
    'formatted' + super
  end

  def scheduled_time_to
    'formatted' + super
  end

  def scheduled_time_formatted
    "#{scheduled_time_from} - #{scheduled_time_to}"
  end
end

request = Request.find(1).cast_as(RequestPresenter)
request.scheduled_time_formatted # => 'time to - time from' 

scheduled_time_formatted should return 'formatted time to - formatted time from'.

I hope the issue is clear from the above, I have no idea how to describe it in words.

Is this expected behaviour?

My work around for now is as such:

# presenter
module RequestPresenter
  def scheduled_time_from_formatted
    'formatted ' + scheduled_time_from
  end

  def scheduled_time_to_formatted
    'formatted ' + scheduled_time_to
  end

  def scheduled_time_formatted
    "#{scheduled_time_from_formatted} - #{scheduled_time_to_formatted}"
  end
end

request = Request.find(1).cast_as(RequestPresenter)
request.scheduled_time_formatted # => 'formatted time to - formatted time from' 

Consider alternate method names

Currently the standard lib Forwardable and ActiveSupport provide delegate methods.

Perhaps a fallback to cast would make sense to prevent confusion.

get super_delegate to work with more than one pass

Currently the super_delegate added in Casting::Super will endlessly loop if multiple methods of the same name are used.

NoMethodError undefined method `cast_as`

There is a high chance I'm just using the library wrong, but here goes:

class User < ActiveRecord::Base
  include Casting::Client
end

module Customer; end

user = User.last
user.cast_as(Customer) # => NoMethodError

This is on Ruby 1.9.3.

Examples

@saturnflyer can you verify this line in the example is correct?
https://github.com/saturnflyer/casting/blob/master/examples/activation.rb#L26

Seems to be calling back to Activation... Would you mind explaining the reasoning behind that?

optional Array/Set extension to allow casting all members of a collection

What do you think of the idea of adding an optionally required extension for Array and Set to allow this:

[thing_1, thing_2 ... ].cast_members_as(ThingPresenter)

It would return a new array where each member has been cast as a ThingPresenter.

Out of scope of casting or a consideration?

Allow arguments to be passed into the `call` method

Currently the Delegation object requires arguments be given using with. Allowing arguments with call would remove surprising behavior.

how to cast_as rspec doubles?

You might not consider this a casting issue, if so, please close.

If I use a double and somewhere along the way it gets cast_as it fails because of course the double does not have the Casting::Client. Do you know of a work around?

# role
class Cancellable
  def cancel
  end
end

def cancel(order)
  order.cast_as(Cancellable)
  order.cancel
end

order = double('order')

order.should_receive(:cancel)

cancel(order)
# => Double 'order' received unexpected messgae :cast_as

Make Class-level casting (refinements) threadsafe

There is also a concern about recursive class casting. This might be an edge-case, but it seems worthwhile to think about.