Hello Friends...
Interviews are being very tough these days as a vast competition in the market. New technologies releasing each moment to make it more competitive. And as you know Ruby on Rails is a most demanded Domain these days. Here I have collected some Interview Questions and their Answers from different sources. I have prepared this keeping in view all the ROR Lovers. Hope this will be helpful for all Junior level Interview attending candidates.
First of all let let me give a small introduction about Ruby on Rails.
Ruby on Rails is a dynamic & reflective object oriented programming language that includes syntex inspired by Perl and Smalltalk like features. Ruby was first designed & developed by Yukihiro "Matz" Matsumoto in Japan in the mid 1990s. It was written in C as a single pass interpreted language. The language specification for Ruby were developed by the Open Standards Promotion Center of the Information Technology Promotion Agency (A Japanese Government Agency) for submission to the Japanese Industrial Standards Committee and then to the International Organization for Standardization.
Question & Answer
1. In which Programming language was Ruby written?
A. Ruby was written in C language and Ruby on Rails written in Ruby.
2. Why Ruby on Rails?
A. There are lots of advantage of using Ruby on Rails.
(i) DRY Principal( Don’t Repeat Yourself):
It is a principle of software development aimed at reducing repetition
of code. “Every piece of code must have a single, unambiguous
representation within a system”
(ii) Convention over Configuration:
Most web development framework for .NET or Java force you to write
pages of configuration code. If you follow suggested naming conventions,
Rails doesn’t need much configuration.
(iii) Gems and Plugins:
RubyGems is a package manager for the Ruby programming language that
provides a standard format for distributing ruby programs and library.
Plugins:
A Rails plugin is either an extension or a modification of the core
framework. It provides a way for developers to share bleeding-edge ideas
without hurting the stable code base. We need to decide if our plugin
will be potentially shared across different Rails applications.
(iv) Scaffolding:
Scaffolding is a meta-programming method of building database-backend
software application. It is a technique supported by MVC frameworks, in
which programmer may write a specification, that describes how the
application database may be used. There are two type of scaffolding:
-static: Static scaffolding takes 2 parameter i.e your controller name and model name.
-dynamic: In dynamic scaffolding you have to define controller and model one by one.
(v) Rack Support:
Rake is a software task management tool. It allows you to specify tasks
and describe dependencies as well as to group tasks in a namespace.
(vi) Metaprogramming: Metaprogramming techniques use programs to write programs.
(vii) Bundler:
Bundler is a new concept introduced in Rails 3, which helps you to
manage your gems for application. After specifying gem file, you need to
do a bundle install.
(viii) Rest Support.
(ix) Action Mailer
3. What is MVC? and How it Works?
A. MVC basically indicates Model-View-Controller. And MVC used by many languages like PHP, Perl, Python etc. Generally MVC works like this:
Request first
comes to the controller, controller finds and appropriate view and
interacts with model, model interacts with your database and send the
response to controller then controller based on the response give the
output parameter to view.
4. How many types of relationships does a Model has?
A. (i) has_one
(ii) belongs_to
(iii) has_many
(iv) has_many :through
5. What is Ruby Gems?
A. Ruby Gem is a software package, commonly called a "gem". Gem contains a packaged Ruby application or library. The Ruby Gems software itself allows you to easily download, install and manipulate gems on your system.
6. What is Session and Cookies?
A. Session is used to store user information on the server side where as Cookies are used to store the information in the client side.
7. What is a symbol and how it differs from variable?
A. Symbol in Ruby is basically the same thing as symbol in the real world. It is used to represent or name something. Symbols are very commonly used to represent some kind of state, for example
order.status = :canceled
order.status = :confirmed
Variables and Symbols are different things. A variable points to different kind of data. In Ruby, a symbol is more like a string than a variable.
In Ruby, a string is mutable, where as a symbol is immutable. That means that only one copy of a symbol needs to be created. symbols are often used as the equivalent to enums in Ruby, as well as keys to a dictionary (hash).
8. What is the difference between Symbol and String in Ruby?
A. -The symbol in Ruby on rails act the same way as the string but the
difference is in their behaviors that are opposite to each other.
-The difference remains in the object_id, memory and process time for both of them when used together at one time.
-Strings are considered as mutable objects. Whereas, symbols, belongs to the category of immutable.
-Strings
objects are mutable so that it takes only the assignments to change the
object information. Whereas, information of, immutable objects gets
overwritten.
-String objects are written like
p: “string object jack”.object_id #=>2250 or
p: “string object jack”.to_sym.object_id #=> 2260, and
p: “string object jack”. to_s_object_id #=> 2270
-Symbols
are used to show the values for the actions like equality or
non-equality to test the symbols faster then the string values.
9. What is the basic difference between GET and POST method?
A. GET is
basically for just getting (retrieving) the data, whereas POST may used to do multiple things, like storing or updating data, or ordering a product, or
sending E-mail etc.
10. What id the difference between Static and Dynamic Scaffolding?
A. The Syntax of Static Scaffold is like this: ruby script/generate scaffold Home New
Where New is the model and Home is your controller, In this way static scaffold takes 2 parameter i.e your controller name and model
name, whereas in dynamic scaffolding you have to define controller and
model one by one.
11. What is ORM Rails ?
A. ORM stands for Object-Relationship-Model, it means that your Classes are mapped to table in the database and Objects are directly mapped to the rows in the table.
12. Does Ruby supports Multiple Inheritance?
A. No, Ruby supports only single Inheritance.
13.Is there any alternative of Multiple inheritance in Ruby? Please Explain.
A. Yes, Ruby offers a very neat alternative concept called mixin. Modules can be
imported inside other class using mixin. They are then mixed-in with the
class in which they are imported.
14. What is Bundler?
A. Bundler is a new concept introduced in Rails3, which helps to you manage
your gems for the application. After specifying gems in your Gemfile,
you need to do a bundle install. If the gem is available in the system,
bundle will use that else it will pick up from the rubygems.org.
15. What are class variables? How do you define them?
A. Class variables are created using the @@ prefix to denote the variable as class level.
It works just like any other variable, however in the case of
inheritance it works more like a static variable that is accessed across
all variable instances.
16. Does Ruby support constructors? How are they declared?
A. Constructors are supported in Ruby. They are declared as the method
initialize, shown below. The initialize method gets called automatically when Class.new is called.
17. What is the purpose of Yield in Ruby?
A. Ruby provides a
yield statement that eases the creation of iterators.
The first thing I noticed was that its behavior is different from the
C# yield statement (which I knew from before).
Ruby's yield statement gives control to a user specified block from the method's body. A classic example is the
Fibonacci Sequence:
class NumericSequences
def fibo(limit)
i = 1
yield 1
yield 1
a = 1
b = 1
while (i < limit)
t = a
a = a + b
b = t
yield a
i = i+1
end
end
...
end
The
fibo method can be used by specifying a block that will be executed each time the control reaches a
yield statement. For example:
irb(main):001:0> g = NumericSequences::new
=> #<NumericSequences:0xb7cd703c>
irb(main):002:0> g.fibo(10) {|x| print "Fibonacci number: #{x}\n"}
Fibonacci number: 1
Fibonacci number: 1
Fibonacci number: 2
Fibonacci number: 3
Fibonacci number: 5
Fibonacci number: 8
Fibonacci number: 13
Fibonacci number: 21
Fibonacci number: 34
Fibonacci number: 55
Fibonacci number: 89
18. What is the difference between Render & Redirect?
A. -Redirect is a method that is used to issue the error message in case
the page is not found or it issues a 302 to the browser. Whereas, render
is a method used to create the content.
-Redirect is used to
tell the browser to issue a new request. Whereas, render only works in
case the controller is being set up properly with the variables that
needs to be rendered.
-Redirect is used when the user needs to
redirect its response to some other page or URL. Whereas, render method
renders a page and generate a code of 200.
-Redirect is used as:
redirect_to: controller => ‘users’, :action => ‘new’
-Render is used as:
render: partial
render: new -> this will call the template named as new.rhtml without the need of redirecting it to the new action.
19. How do you define Class Variable, Instance Variable and Global Variable in Ruby?
A. Ruby Class Variables
Class variables begin with @@ and must be initialized before they can be used in method definitions.
Referencing an uninitialized class variable produces an error. Class
variables are shared among descendants of the class or module in which
the class variables are defined.
Overriding class variables produce warnings with the -w option.
Here is an example showing usage of class variable:
#!/usr/bin/ruby
class Customer
@@no_of_customers=0
def initialize(id, name, addr)
@cust_id=id
@cust_name=name
@cust_addr=addr
end
def display_details()
puts "Customer id #@cust_id"
puts "Customer name #@cust_name"
puts "Customer address #@cust_addr"
end
def total_no_of_customers()
@@no_of_customers += 1
puts "Total number of customers: #@@no_of_customers"
end
end
# Create Objects
cust1=Customer.new("1", "John", "Wisdom Apartments, Ludhiya")
cust2=Customer.new("2", "Poul", "New Empire road, Khandala")
# Call Methods
cust1.total_no_of_customers()
cust2.total_no_of_customers()
Here @@no_of_customers is a class variable. This will produce following result:
Total number of customers: 1
Total number of customers: 2
Ruby Instance Variables
Instance variables begin with @. Uninitialized instance variables have the value
nil and produce warnings with the -w option.
Here is an example showing usage of Instance Variables.
#!/usr/bin/ruby
class Customer
def initialize(id, name, addr)
@cust_id=id
@cust_name=name
@cust_addr=addr
end
def display_details()
puts "Customer id #@cust_id"
puts "Customer name #@cust_name"
puts "Customer address #@cust_addr"
end
end
# Create Objects
cust1=Customer.new("1", "John", "Wisdom Apartments, Ludhiya")
cust2=Customer.new("2", "Poul", "New Empire road, Khandala")
# Call Methods
cust1.display_details()
cust2.display_details()
Here @cust_id, @cust_name and @cust_addr are instance variables. This will produce following result:
Customer id 1
Customer name John
Customer address Wisdom Apartments, Ludhiya
Customer id 2
Customer name Poul
Customer address New Empire road, Khandala
Ruby Global Variables
Global variables begin with $. Uninitialized global variables have the value
nil and produce warnings with the -w option.
Assignment to global variables alters global status. It is not recommended to use global variables. They make programs cryptic.
Here is an example showing usage of global variable.
#!/usr/bin/ruby
$global_variable = 10
class Class1
def print_global
puts "Global variable in Class1 is #$global_variable"
end
end
class Class2
def print_global
puts "Global variable in Class2 is #$global_variable"
end
end
class1obj = Class1.new
class1obj.print_global
class2obj = Class2.new
class2obj.print_global
Here $global_variable is a global variable. This will produce following result:
NOTE: In Ruby you CAN access value of any variable or constant by putting a hash (#) character just before that variable or constant.
Global variable in Class1 is 10
Global variable in Class2 is 10
(Source: h
ttp://www.tutorialspoint.com/ruby/ruby_variables.htm)
20. What is Gemfile and Gemfile.lock?
A. The
Gemfile is where you specify which gems you want to use, and lets you specify which versions.
The
Gemfile.lock file is where Bundler records the exact
versions that were installed. This way, when the same library/project
is loaded on another machine, running
bundle install will look at the
Gemfile.lock and install the exact same versions, rather than just using the
Gemfile
and installing the most recent versions. (Running different versions on
different machines could lead to broken tests, etc.) You shouldn't ever
have to directly edit the lock file.
Get more Explanations on Gem file
here.
21. What is the difference between puts and print ?
A. puts appends a new line and outputs each argument to a new line but
print doesn't append anything and seems to separate arguments by a space.
22. What is has_many ?
A. 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. For example, in an
application containing customers and orders, the customer model could be
declared like this:
class Customer < ActiveRecord::Base
has_many :orders
end
The corresponding migration might look like this:
class CreateCustomers < ActiveRecord::Migration
def change
create_table :customers do |t|
t.string :name
t.timestamps
end
create_table :orders do |t|
t.belongs_to :customer
t.datetime :order_date
t.timestamps
end
end
end
(Source:
http://guides.rubyonrails.org/association_basics.html)
23. How to use sql db or mysql db without defining it in the database.yml?
A. You can use ActiveRecord anywhere
require “rubygems”
require “active_record”
ActiveRecord::Base.establish_connection({
:adapter=> ‘postgresql’, :user=>’foo’, :password=> ‘abc’, :database=>’whatever’})
24. How you run your Rails application without creating databases?
A. You can run your application by uncommenting the line in environment.rb
path=> rootpath conf/environment.rb
config.frameworks- = [action_web_service, :action_mailer, :active_record
25. What are the servers supported by ruby on rails?
A. Ruby Supports a number of Rails servers (Mongrel, WEBRICK, PHUSION, Passenger, etc..depending on the specific platforms).
For each Rails application project, RubyMine provides default Rails run/debug configurations for the production and development environments.
26. Can we use two databases into a single application?
A. Yes, Definitely. magic multi-connections allows you to write your model once, and use them for the multiple rails databases at the same time.
sudo gem install magic_multi_connection. After installing this gem,
just add this line at bottom of your environment.rb require
“magic_multi_connection”
27. What is scope?
A. Scopes are nothing more than SQL scope fragments. By using these
fragments one can cut down on having to write long queries each time you
access content.
28. Can you give an example of a class that should be inside the lib folder?
A. Modules are often placed in the lib folder.
29. Where should you put code that is supposed to run when your application launches?
A. In the rare event that your application needs to run some code before
Rails itself is loaded, put it above the call to require ‘rails/all’ in
config/application.rb.
30. What deployment tool do you use?
A. Capistrano is a popular deployment tool, it allows developers to push code from their desktop to the servers. you can also use chef as a deployment tool for your project.
31. What is a filter? When it is called?
A. Filters are methods that are called either before/after a controller action is called.
32. What is the difference between a plugin and a gem?
A. A gem is just ruby code. It is installed on a machine and it’s available for all ruby applications running on that machine.
Rails, rake, json, rspec — are all examples of gems.
Plugin is also ruby code but it is installed in the application folder and only available for that specific application.
Sitemap-generator, etc.
In general, since Rails works well with gems you will find that you
would be mostly integrating with gem files and not plugins in general.
Most developers release their libraries as gems.
33. How many types of callbacks available in ROR?
A. Different types of callbacks available in ROR like:
(1) before_validation
(2) before_validation_on_create
(3) validate_on_create
(4) after_validation
(5) after_validation_on_create
(6) before_save
(7) before_create
(8) after_create
(9) after_save
34. What is request.xhr?
A. A request.xhr tells the controller that the new Ajax request has come, It always return TRUE or FALSE.
35. How to serialize data with YAML?
A. YAML is a
straight forward machine parsable data serialization format, designed
for human readability and interaction with scripting language such as
Perl and Python.
YAML is optimized for data serialization, formatted dumping, configuration files, log files, internet messaging and filtering.
36. What are Filters?
A. Filters are
methods that run “before”, “after” or “around” a controller action.
Filters are inherited, so if you set a filter on Application Controller,
it will be run on every controller in your application.
37. Explain the Naming Convention in Rails.
A. Variables: Variables are named where all letters are lowercase and words are separated by underscores. E.g: total, order_amount.
Class and Module: Classes and modules uses MixedCase and have no underscores, each word starts with a uppercase letter. Eg: InvoiceItem
Database Table:
Table name have all lowercase letters and underscores between words,
also all table names to be plural. Eg: invoice_items, orders etc
Model: The model is named using the class naming convention of unbroken MixedCase and always the singular of the table name.
For eg: table
name is might be orders, the model name would be Order. Rails will then
look for the class definition in a file called order.rb in /app/model
directory. If the model class name has multiple capitalized words, the
table name is assumed to have underscores between these words.
Controller:
controller class names are pluralized, such that OrdersController
would be the controller class for the orders table. Rails will then look
for the class definition in a file called orders_controlles.rb in the
/app/controller directory.
38. What is Active Record?
A. Active Record are like Object Relational Mapping(ORM), where classes are
mapped to table and objects are mapped to colums in the table.
39. What is a Range in Ruby?
A. The first and perhaps most natural use of ranges is to express a
sequence. Sequences have a start point, an end point, and a way to
produce successive values in the sequence. In Ruby, these sequences are
created using the ".." and "..." range operators. The two dot form
creates an inclusive range, and the three-dot form creates a range that
excludes the specified high value. In Ruby ranges are not represented
internally as lists: the sequence 1..100000 is held as a
Range object containing references to two
Fixnum objects. Refer program
p021ranges.rb. If you need to, you can convert a range to a list using the
to_a method.
- (1..10).to_a -> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Ranges implement methods that let you iterate over them and test their contents in a variety of ways.
-
- =begin
- Sequences have a start point, an end point, and a way to
- produce successive values in the sequence
- In Ruby, sequences are created using the ".." and "..."
- range operators.
- The two dot form creates an inclusive range.
- The three-dot form creates a range that excludes the specified
- high value
- The sequence 1..100000 is held as a Range object
- =end
- digits = -1..9
- puts digits.include?(5)
- puts digits.min
- puts digits.max
- puts digits.reject {|i| i < 5 }
Another use of the versatile range is as an interval
test: seeing if some value falls within the interval represented by the
range. We do this using ===, the case equality operator.
- (1..10) === 5 -> true
- (1..10) === 15 -> false
- (1..10) === 3.14159 -> true
- ('a'..'j') === 'c' -> true
- ('a'..'j') === 'z' -> false
(Source:
http://rubylearning.com/satishtalim/ruby_ranges.html)
40. How can you implement method overloading?
A. You want to create two different versions of a method with the same name: two methods that differ in the arguments they take. However,
a Ruby class can have only one method with a given name (if you define a method with the same name twice, the latter method definition prevails as seen in example
p038or.rb in topic
Ruby Overriding Methods).
Within that single method, though, you can put logic that branches
depending on how many and what kinds of objects were passed in as
arguments.
Here's a Rectangle class that represents a
rectangular shape on a grid. You can instantiate a Rectangle by one of
two ways: by passing in the coordinates of its top-left and bottom-right
corners, or by passing in its top-left corner along with its length and
width. There's only one
initialize method, but you can act as though there were two.
-
-
-
-
- class Rectangle
- def initialize(*args)
- if args.size < 2 || args.size > 3
-
- puts 'This method takes either 2 or 3 arguments'
- else
- if args.size == 2
- puts 'Two arguments'
- else
- puts 'Three arguments'
- end
- end
- end
- end
- Rectangle.new([10, 23], 4, 10)
- Rectangle.new([10, 23], [14, 13])
The above program
p037rectangle.rb
is incomplete from the Rectangle class viewpoint, but is enough to
demonstrate how method overloading can be achieved. Also remember that
the
initialize method takes in a variable number of arguments.
41. What is the difference between '&&' and '||' operators?
A. "&&" has higher precedence than "||" like in most other mainstream languages;
but "or" and "and" in ruby have the same(!) precedence level!
so if you write
(func1 || func2 && func3), it's (func1 || (func2 && func3))
but
(func1 or func2 and func3) is interpreted as ((func1 or func2) and func3)
because of shorcircuiting, if func1 is true, both func2 and func3 won't be called at all in the first example
but in the second example func3 WILL be called!
this difference is subtile enough that I really do not recommend newbies to use "and" and "or" in ruby at all.
42. Why Explanation marks used in Ruby?
A. In general, methods that end in ! indicate that the method will
modify the object it's called on.
Ruby calls these "dangerous methods" because they change state that
someone else might have a reference to. Here's a simple example for
strings:
foo = "A STRING" # a string called foo
foo.downcase! # modifies foo itself
puts foo # prints modified foo
This will output:
a string
In the standard libraries, there are a lot of places you'll see pairs
of similarly named methods, one with the ! and one without. The ones
without are called "safe methods", and they return a copy of the orignal
with changes applied to
the copy, with the callee unchanged. Here's the same example without the !:
foo = "A STRING" # a string called foo
bar = foo.downcase # doesn't modify foo; returns a modified string
puts foo # prints unchanged foo
puts bar # prints newly created bar
This outputs:
A STRING
a string
Keep in mind this is just a convention, but a lot of ruby classes
follow it. It also helps you keep track of what's getting modified in
your code.
43. What is the Purpose of "!" and "?" at the end of method names?
A. It's "just sugarcoating" for readability, but they do have common meanings:
- Methods ending in
! perform some permanent or potentially dangerous change; for example:
Enumerable#sort returns a sorted version of the object while Enumerable#sort! sorts it in place.- In Rails,
ActiveRecord::Base#save returns false if saving failed, while ActiveRecord::Base#save! raises an exception.
Kernel::exit causes a script to exit, while Kernel::exit! does so immediately, bypassing any exit handlers.
- Methods ending in
? return a boolean, which makes the code flow even more intuitively like a sentence — if number.zero? reads like "if the number is zero", but if number.zero just looks weird.
In your example,
name.reverse evaluates to a reversed string, but only after the
name.reverse! line does the
name variable actually
contain the reversed name.
name.is_binary_data? looks like "is
name binary data?".
:) Confused ?
Just remember it in simple
In Ruby the
? means that the method is going to return a boolean and the
! modifies the object it was called on. They are there to improve readability when looking at the code.
44. What is Mixin ?
A. Ruby does not suppoprt mutiple inheritance directly but Ruby Modules
have another, wonderful use. At a stroke, they pretty much eliminate the
need for multiple inheritance, providing a facility called a
mixin.
Mixins give you a wonderfully controlled way of adding functionality
to classes. However, their true power comes out when the code in the
mixin starts to interact with code in the class that uses it.
let me give a small example
module A
def a1
end
def a2
end
end
module B
def b1
end
def b2
end
end
class Sample
include A
include B
def s1
end
end
samp=Sample.new
samp.a1
samp.a2
samp.b1
samp.b2
samp.s1
Module A consists of the methods a1 and a2. Module B consists of the
methods b1 and b2. The class Sample includes both modules A and B. The
class Sample can access all four methods, namely, a1, a2, b1, and b2.
Therefore, you can see that the class Sample inherits from both the
modules. Thus you can say the class Sample shows multiple inheritance or
a
mixin.
(Source:
http://www.tutorialspoint.com/ruby/ruby_modules.htm)
45. What is purpose of RJs in Rails ?
A)
RJS
is a template (similar to an html.erb file) that generates JavaScript
which is executed in an eval block by the browser in response to an
AJAX request. It is sometimes used (incorrectly?) to describe the
JavaScript, Prototype, and Scriptaculous Helpers provided by Rails. This may Help you more.
46.
What
is eager loading, lazy loading and over-eager loading?
A)
Generally
three levels are there:
Eager
loading: you
do everything when asked. Classic example is when you multiply two
matrices. You do all the calculations. That's eager loading;
Lazy
loading: you
only do a calculation when required. In the previous example, you
don't do any calculations until you access an element of the result
matrix; and
Over-eager
loading: this
is where you try and anticipate what the user will ask for and
preload it.
For
Example:
Imagine
a page with rollover images like for menu items or navigation. There
are three ways the image loading could work on this page:
Load
every single image required before you render the page (eager);
Load
only the displayed images on page load and load the others if/when
they are required (lazy);
and
Load
only the displayed images on page load. After the page has loaded
preload the other images in the background in
case you need them (over-eager).
47.
How
can you define a constant?
A)
Constants
defined within a class or module can be accessed from within that
class or module, and those defined outside a class or module can be
accessed globally.
Constants
begin with an uppercase letter. Constants may not be defined within
methods. Referencing an uninitialized constant produces an error.
Making an assignment to a constant that is already initialized
produces a warning.
#!/usr/bin/ruby
class Example
VAR1 = 100
VAR2 = 200
def show
puts "Value of first Constant is #{VAR1}"
puts "Value of second Constant is #{VAR2}"
end
end
# Create Objects
object=Example.new()
object.show
Here
VAR1 and VAR2 are constant. This will produce following result:
Value of first Constant is 100
Value of second Constant is 200
48.
How
can you call the base class method from inside of its overriden
method?
A)
The A::foo will
call B::bar if
you have an instance of B.
It does not matter if the instance is referenced through a pointer or
a reference to a base class: regardless of this, B's
version is called; this is what makes polymorphic calls
possible. The behavior is not compiler-specific: virtual functions
behave this way according to the standard.
49.
What
is an observer?
A)
Observer
serves as a connection point between models and some other subsystem
whose functionality is used by some of other classes, such as email
notification. It is loose coupling in contract with model callback.
50.
How
can you implement rails observer for multiple models?
A)
Implementing
Rails Observer are simple. You can observe multiple models within a
single observer.
First
you need to generate your observer.
rails g observer Auditor
Then,
in your fresh auditor_observer.rb file define the models you wish
to observe and
then add theafter_create callback.
class AuditorObserver < ActiveRecord::Observer
observe :model_foo, :model_bar, :model_baz
def after_create(record)
#do something with `record`
end
end
And
It should work.
51.
What
is the difference between Observers & Callbacks ?
A)
A
callback is more short lived: You pass it into a function to be
called once. It's part of the API in that you usually can't call the
function without also passing a callback. This concept is tightly
coupled with what the function does. Usually, you can only pass a
single callback..
Example:
Running a thread and giving a callback that is called when the thread
terminates.
An
observer lives longer and it can be attached/detached at any time.
There can be many observers for the same thing and they can have
different lifetimes.
Example:
Showing values from a model in a UI and updating the model from user
input.
52.
What
is a sweeper in rails?
A)
Sweepers
are the terminators of the caching world and responsible for expiring
caches when model objects change. They do this by being
half-observers, half-filters and implementing callbacks for both
roles. You can get more Informations here.
53.
How
can you list all routes for an application?
A)
By
writing rake
routes
in the terminal we can list out all routes in an application.
54. Is it possible to embed partial views inside layouts? How?
A) Yes it is possible. You Embed partial views inside the file /app/views/layout/application.html.erb and then whenever you render any page this layout is merged with it.
55.
What
is rake?
A)
rake
is command line utility of rails. “Rake
is Ruby Make, a standalone Ruby utility that replaces the Unix
utility ‘make’, and uses a ‘Rakefile’ and .rake files
to build up a list of tasks. In Rails, Rake is used for common
administration tasks, especially sophisticated ones that build off of
each other.”
Putting
in simple word : “rake
will execute different tasks(basically a set of ruby code) specified
in any file with .rake extension from comandline.”
All
commands available for rails are listed here.
56. What is Polymorphic Association?
A) 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.
Friends i tried to cover up as much as possible questions and answers over here in this page. Hope you guys like it. I will keep updating more questions and answers. Keep in touch. All the best.
(Note: Interviewer may not ask the exact questions mentioned here in this section. I have just tried to give some overall idea what you may face during the time of Interview. Also try to google out more articles like this. More opinions, suggestions, Q&A's will be always highly appreciable.)
Candidates searching for a
Business Analyst Position may also like
this set of Interview Questions
Sources used to Prepare this page:
http://ruby.megasolutions.net/
Megasolution
http://anilpunjabi.tumblr.com/post/25948339235/ruby-and-rails-interview-questions-and-answers
Anils Link
http://theprofessionalspoint.blogspot.in/2013/02/basic-ruby-on-rails-ror-interview.html
The Professional Point
http://puneetpandey.com/tag/ruby-on-rails-interview-questions/
Puneets Blog
http://interviewquestionsanswers.org/forum/topic-1005-ruby-on-rails-interview-questions-and-answers-page-1.html
Interview Questions & Answers
http://blog.sandeep.me/2012/05/ruby-on-rails-interview-questions.html
Sandeeps Blog
http://careerride.com/ruby-on-rails-interview-questions.aspx
Career Ride
http://www.psteiner.com/2013/02/preparing-for-ruby-on-rails-job.html
Ruby On Rails Job
http://meet2ravi.blogspot.in/2012/12/ruby-question-and-answer.html
Ravi's Blog
http://www.tutorialspoint.com
Tutorial Point
http://rubylearning.com
Ruby Learning
http://www.
stackoverflow.comStack Overflow
ruby.railstutorial.org/Rails Tutorial
guides.rubyonrails.orgRuby On Rails Guide
www.sitepoint.com/learn-ruby-on-rails/
Site Point
www.rubyonrailstutorials.comRuby On Rails Tutorial
And many others.
Yes Don't forget to Comment and share if these collections helpful for you. :)
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