String

Question 1

How to return the first or last symbol of a string?

Answer 1

‘string’[0] #=> ‘s’
‘string’[-1] #=> ‘g’
‘string’[1..-1] #=> ‘tring’

Question 2

How to convert a string to an array of characters? 2 ways

Answer 2

‘hello’.chars #=> [“h”, “e”, “l”, “l”, “o”]

‘hello’.split(‘’) #=> [“h”, “e”, “l”, “l”, “o”]

Question 3

How to find the number of a given character in a string?

Answer 3

‘hello’.count(‘h’) #=> 1

Question 4

What is scan method?

Answer 4

Return an array of each matching of given expression

“A aaaa bb c”.scan(/[a-z]+/) #=> [“aaaa”, “bb”, “c”]

Question 5

Why do we need format method? And how to use it?

Answer 5

puts format("A string %s, with minimum 10 signs %10s, with max 2 letters %.2s ", "hello",'dd', 'aaa')
#=> A string hello, with minimum 10 signs         dd, with max 2 letters aa

puts format("An integer: %i", 15)
puts format("A float: %f", 3.1415)

Question 6

How to calculate number/letter count in the string?

Answer 6

‘kdakdwa12345’.count ‘0-9’ #=>5

‘abc21321’.count ‘a-z’ # => 3

Question 7

How to replace part of the string by regexp?

Answer 7

'hello a b c'.sub(/hello/, '\1 adwadwa')
# => " adwadwa a b c"

Question 8

How to change string character case into opposite?

Answer 8

'daDSwa'.swapcase
# => "DAdsWA"

Question 9

How to increment string in ruby? ( ‘Z01’ -> ‘Z02’)

Answer 9

str.succ

Question 10

Why do we need to freeze string?

Answer 10

Strings in Ruby are mutable, which means you can change them. You can make a string immutable by using the freeze method. Trying to modify a frozen string will raise an exception.

str.freeze
str[0] = “”

RuntimeError: can’t modify frozen String

Question 11

Why do ween need to freeze string?

Answer 11

It allows us to allocate space because the same frozen string use the same object id

a = 'hello'
b = 'hello'

different
p a.object_id
p b.object_id

a = 'hello'.freeze
b = 'hello'.freeze

the same
p a.object_id
p b.object_id

Question 12

What is better to use symbol or string?

Answer 12

Symbol has better performance, so if it’s possible would be better to send symbols.

Question 13

How to use multiline strings?

Answer 13

1. here document or heredoc,
   hello = &laquo_space;DOC
   ddd
   ddd
2. x = %q{This is a test
   of the multi
   line capabilities}