Questions All Ruby Developers Should Be Able to Answer!
* What is a class?
- Classes are a blue-print for constructing computer models for real or virtual objects.
- Classes hold data, have methods that interact with data, and are used to instantiate objects.
* What is an object?
- An instance of a class. To some it's also the root class in ruby.Classes themselves descend from the object root class.
* What is a module? Can you tell me the difference between classes and modules?
- Modules serve as a mechanism for namespaces.
-Also, modules provide as a mechanism for multiple inheritance via mix-ins and cannot be instantiated like classes can.
* Can you tell me the three levels of method access control for classes and modules? What do they imply about the method?
- All methods, no matter the access control can be accessed within the class But what about outside callers?
- Public methods enforce no access control -- they can called in any scope.
- Protected methods are only accessible to other objects of the same class.
- Private methods are only accessible within the context of the current object.
* There are three ways to invoke a method in ruby. Can you give me at least two?
- There is the dot operator (object.object_id)
- There is the Object#send method (object.send(:object_id))
- method(:foo).call (object.method(:object_id).call
* Explain this ruby idiom: a ||= b
A common idiom that strong ruby developers use all the time.
A || a =b this means that a == b when a == false.
self always refers to the current object. But this question is more difficult than it seems because Classes are also objects in ruby.
* What is difference between unit, functional, integration testing?
- Unit testing, simply put, is testing methods -- the smallest unit in objectoriented programming. Strong candidates will argue that it allows a developer to flesh out their API before it's consumed by other systems in the application.The primary way to achieve this is to assert that the actual result of the method matches an expected result.
* Tell me about the Ruby Object Model.
- Almost everything in Ruby is an object. The Ruby object model explains why that is:
- http://www.hokstad.com/ruby-object-model
* What happens when you include a module on a class? What about extending a module on a class? Why?
* What happens when you include a module on an instance? What about extending a module on an instance? Why?
* What is a Proc?
- People confuse procs with blocks. Essentially, Procs are anonymous methods( or nameless functions) containing code. They can be placed inside a variable and passed around like any other object or scalar value. They are created by Proc.new, lambda, and blocks(invoked by the yield keyword).
* What is a named scope?
- A scope is a subset of a collection. Sounds complicated? It isn't. Imagine this:
You have Users. Now, some of those Users are subscribed to your newsletter. You marked those who receive a newsletter by adding a field to the Users Database (user.subscribed_to_newsletter = true). Naturally, you sometimes want to get those Users who are subscribed to your newsletter.
You could, of course, always do this:
User.where(subscribed_to_newsletter: true).each do #something
Instead of always writing this you could, however, do something like this.
#File: users.rb
class User < ActiveRecord::Base
scope :newsletter, where(subscribed_to_newsletter: true)
#yada yada
end
This allows you to access your subscribers by simply doing this:
User.newsletter.each do #something
This is a very simple example but in general scopes can be very powerful tools to easy your work.
Check out this link: API Desciption
http://stackoverflow.com/questions/4869994/what-is-scope-named-scope-in-rails
* What is the difference between includes and joins.
- :joins joins tables together in sql, :includes eager loads associations to avoid the n+1 problem (where one query is executed to retrieve the record and then one per association which is loaded).
I suggest you read their sections in Rails Guides to get more info:
-http://stackoverflow.com/questions/4861416/whats-the-difference-between-includes-and-joins-in-activerecord-query
* How would you implement basic caching?
- http://guides.rubyonrails.org/caching_with_rails.html
* How about partial page caching?
- http://guides.rubyonrails.org/caching_with_rails.html
* What is a polymorphic association?
- In Rails, Polymorphic Associations allow an ActiveRecord object to be associated with multiple ActiveRecord objects. A perfect example for that would be comments in a social network like Facebook. You can comment on anything on Facebook like photos, videos, links, and status updates. It would be impractical if you were to create a comment model (photos_comments, videos_comments, links_comments) for every other model in the application. Rails eliminates that problem and makes things easier for us by allowing polymorphic associations.
-http://terenceponce.github.io/blog/2012/03/02/polymorphic-associations-in-rails-32/
* What is a has and belongs to many association?
- A belongs_to association sets up a one-to-one connection with another model, such that each instance of the declaring model "belongs to" one instance of the other model.
- A has_many association indicates a one-to-many connection with another model. You'll often find this association on the "other side" of a belongs_to association. This association indicates that each instance of the model has zero or more instances of another model.
http://guides.rubyonrails.org/association_basics.html
* What is Rack
- Rack is a nice Ruby-fied replacement for CGI. Rack sits between all the frameworks (Rails, Sinatra, Rulers) and all the app servers (thin, unicorn, Rainbows, mongrel) as an adapter.
Rack is a convenient way to build your Ruby app out of a bunch of thin layers, like a stack of pancakes. The layers are called middleware. Or pancakes, why not?
-http://codefol.io/posts/What-is-Rack-A-Primer
* What is the purpose of Active Record?
- Active Record serves as a way to retrieve data from the database.
* What is the purpose of Active Support?
-
* What would you store in a Session?
-Rails uses a CookieStore to handle sessions. What it means is that all the informations needed to identify a user's session is sent to the client and nothing is stored on the server. When a user sends a request, the session's cookie is processed and validated so rails, warden, devise, etc. can figure out who you are and instantiate the correct user from the database. Cookies are how server can remember who you are from one request to another. Everytime you send a request to a server, you send every cookie you have for that domain. Nothing new here. A session cookie is signed and encrypted (encryption is new in Rails 4) then sent to the browser. That cookie is actually an hash that would look like this if you run something like Warden and Devise:
- http://www.andylindeman.com/2013/02/18/decoding-rails-session-cookies.html
* Explain is as much possible detail what happens when you make a request in your browser.
* Explain REST
* What is a HTTP response for?
* What is a HTTP request for?
* What does it mean for a request to be idempotent? What types of requests are idempotent?
* What are cookies for?
* Explain inner, outer, left and right joins.
[1]: https://gist.github.com/austenito/5810643
[3]: http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html
tangentwithtanner
dededos
prguitarman
stormborns
kaledo-art
baratheonpilled
jbbartram-illu