Ostend - Creative support for object initializers that take hashes. Why can't I just initialize these instance variables from this hash? Now you can.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.


We All Have Hashes

And at some point we just want to:

hash = { :name => 'Twilight Sparkle', :enemy => 'Ahuizotl', :size => 'little' }

my_correctly_sized_pony = SizedPony.new(hash)

  # => 'Twilight Sparkle'

my_correctly_sized_pony.enemy = 'Queen Chrysalis'
  # => 'Queen Chrysalis'

We can use OpenStruct, but then we can't directly inherit from the real class!

Why in Ponyland is that so hard?

It's Not Hard

class SizedPony < Pony
  include Ostend

  def initialize(hash)

Two new lines. That's it! And nothing is forced on you.

If you don't want to instantiate the variables in new(), you don't have to. You can call ostendify() anywhere you like.

There's Always More

I have added a few additional features:

Accessor Type control

By default, Ostend creates attr_accessors.

You say you'd prefer writers (or readers)? Set @ostend_attr_type before you call ostendify()

  pony.ostend_attr_type = :writer # or = :reader
  pony.ostendify( hash )

    # => NoMethodError

Attribute Filter

Whitelist hash keys for attributes that you don't want assigned You don't want your ponies to have enemies? Set @ostend_attr_filter before you call ostendify()

  pony.ostend_attr_filter = [:name, :size]
  # Now Ostend happily and silenty drops the other hash keys
  pony.ostendify( hash )

    # => NoMethodError

Strict Assignment

Lastly, you can force exceptions if you don't want arguments other that what you specified in the filter.

  pony.ostend_attr_filter = [:name, :size]
  pony.ostend_strict      = true
  # Now Ostend throws a hissy fit when you attempt instantiaion

  pony.ostendify( hash )
    # => Exception :: The following are not allowed attributes: :enemies

Still More

Combine this with ActiveRecord validations, and you can do some awesome stuff.

There are other gem combinations that could be really killer.

Let Me Know What You Discover!


Ostend is meant to be a simple, Unix-like tool that doesn't get in your way. It helps you maintain your sanity and SRP.

But you can just use OpenStruct as your parent.

Sure but then you can't inherit from what the class you really should be inheriting from.

But you can create an abstraction layer between OpenStruct and your class

Yup! Except this is easier and cleaner (imo).

Using this as a mix in we are able to maintain a meaningful class structure while exposing the hash keys as viable and visable methods. This helps to keep your Classes focused on what they need to do. They don't have to run around, crazily setting accessors nor instance variables.

The accessors are also created on each individual instance of your class. In this way, you can have object of the same class with different configurations.

You're Doing It All Wrong!

There are definitely alternative ways of getting to this behavior. I just like this because it's simple and has neither bells nor whistles. There are awesome gems like Virtus solnic/virtus that can enable a bunch of what I do here.

However, Virtus requires full attribute definition as part of it's explicit goal.

But this promotes horrifyingly bad practices!

I give my users the benefit of the doubt. I trust they will make good decisions and follow best practices.

If you really dislike the practices that this promotes, let me know and we can work to make it better

Where Is This Going

I have a few ideas for expansion.

  1. Enabling class level accessor creation
  2. Create the Ostend variable as class_level variables to allow easier control over the entire class
  3. I could start to get into crazy, ActiveRecord relation assignments

However, I'm not sure how far I will go as it's current form is just about the size I want it to be.

Contributing and Feedback

Please Do Contribute! Normal commit message and pull request rules apply.

Thoughts? Comments? Please let me know if you're using this! I'd love to hear how and why you're using it!


Codeship build staus