Quiz - August

Question 1

How can you run some ruby script without IRB or ruby file?

Answer 1

We can use the -e tag against the ruby command.

Example :

> ruby -e ‘puts “Ruby programming”’

Question 2

What would be the output of the code?

puts “This statement comes later”
BEGIN {
puts “This statement will be printed in the beginning”
}

Answer 2

This statement will be printed in the beginning

This statement comes later

Question 3

It is possible to print multi-line strings using print in Ruby?

Answer 3

yes

We can use EOF or EOC with print

Question 4

What would be the output?

”[%s]” % “same old drag”

Answer 4

”[%s]” % “same old drag”

# => “[same old drag]”

Quick string interpolation

Question 5

x = %w{p hello p}
“%s%s>” % x

is this valid?

Answer 5

yes
# => "<p>hello</p>"

Question 6

a = %w{a b}
b = %w{c d}
what is the output of this code?
[a + b]                             
[*a + b]

Answer 6

[a + b] # => [[“a”, “b”, “c”, “d”]]
[*a + b] # => [“a”, “b”, “c”, “d”]

Question 7

does = is = { true => ‘Yes’, false => ‘No’ }

is this valid ?

does[10 == 50]
is[10 > 5]

Answer 7

It’s rare you see anyone use non-strings or symbols as hash keys. It’s totally possible though, and sometimes handy :

does = is = { true => ‘Yes’, false => ‘No’ }
does[10 == 50] # => “No”
is[10 > 5] # => “Yes”

Question 8

require ‘rubygems’
require ‘activemerchant’
require ‘date’

If we have more required modules, shall we use any shortcut code for this?

Answer 8

you can take this to extremes using Ruby’s enumerators to perform similar operations multiple times. Consider requiring multiple files, for instance:

%w{rubygems daemons eventmachine}.each { |x| require x }

Question 9

qty = 1
qty == 0 ? ‘none’ : qty == 1 ? ‘one’ : ‘many’

is this valid code?

What would be the output?

Answer 9

“one”

ternary operators can be nested within each other

Question 10

How to skip this error?

for example
h = { :age => 10 }
h[:name].downcase =>Error

Answer 10

yes.
You can use rescue in its single line form to return a value when other things on the line go awry:

h = { :age => 10 }
h[:name].downcase # ERROR
h[:name].downcase rescue “No name” # => “No name”

Question 11

How to delete directories with files in Ruby?

Answer 11

To delete directories, Ruby comes with a handy file utility library called FileUtils that can do the hard work:

require ‘fileutils’
FileUtils.rm_r ‘somedir’

Question 12

money = 9.5
cost = 100

How to convert to “9.50” and “100.00”?

Answer 12

Formatting floating point numbers into a form used for prices can be done with sprintf or, alternatively, with a formatting interpolation:

Question 13

a = %w{a b c d e f g h}
b = [0, 5, 6]

a. values_at(b[0])
a. values_at(b[1])
a. values_at(b[2]) # a , f, g

How to get the values in one shot?

Answer 13

a = %w{a b c d e f g h}
b = [0, 5, 6]
a.values_at(*b).inspect

use explode

Question 14

Which one is correct?

def is_odd(x)
  x % 2 == 0 ? false : true
end

def is_odd(x)
x % 2 != 0
end

Answer 14

Both are correct

Question 15

How to convert “to_boolean” of any value?

Answer 15

!! “hello”
!! nil

double bang

!!"hello" #-> this is a string that is forced into a boolean 
          #   context (true), and then negated (false), and then 
          #   negated again (true)
!!nil     #-> this is a false-y value that is forced into a boolean 
          #   context (false), and then negated (true), and then 
          #   negated again (false)