10. Ruby Data Types

1# Single quotes (literal)
2name = 'John Doe'
3
4# Double quotes (allows interpolation and escape characters)
5greeting = "Hello, #{name}!"  # => "Hello, John Doe!"
6
7# Multi-line strings
8description = <<~TEXT
9  This is a multi-line string.
10  It preserves line breaks.
11  Very useful for long text.
12TEXT
13
14# Common string methods
15name = "  Ruby on Rails  "
16
17name.length        # => 17
18name.upcase        # => "  RUBY ON RAILS  "
19name.downcase      # => "  ruby on rails  "
20name.capitalize    # => "  ruby on rails  "
21name.strip         # => "Ruby on Rails"
22name.split(" ")    # => ["Ruby", "on", "Rails"]
23name.include?("Ruby") # => true
24name.gsub("Rails", "Framework") # => "  Ruby on Framework  "

1user = "Alice"
2age = 25
3
4# Using interpolation (double quotes required)
5message = "#{user} is #{age} years old"
6# => "Alice is 25 years old"
7
8# You can include any Ruby expression
9price = 19.99
10puts "Total: $#{'%.2f' % (price * 1.1)}"
11# => "Total: $21.99"

1# Integers
2count = 42
3negative = -17
4big_number = 1_000_000  # Underscores for readability
5
6# Floats (decimal numbers)
7price = 19.99
8pi = 3.14159
9
10# Arithmetic operations
1110 + 3    # => 13 (addition)
1210 - 3    # => 7 (subtraction)
1310 * 3    # => 30 (multiplication)
1410 / 3    # => 3 (integer division)
1510.0 / 3  # => 3.333... (float division)
1610 % 3    # => 1 (modulo/remainder)
1710 ** 3   # => 1000 (exponentiation)
18
19# Useful methods
20-5.abs         # => 5
213.14.round     # => 3
223.14.ceil      # => 4
233.14.floor     # => 3
245.even?        # => false
255.odd?         # => true
2610.between?(5, 15) # => true

1is_active = true
2is_deleted = false
3
4# In Ruby, only nil and false are falsy
5# Everything else is truthy (including 0 and empty strings)
6
7if 0
8  puts "0 is truthy in Ruby!"
9end
10
11# Comparison operators
125 == 5     # => true (equality)
135 != 3     # => true (not equal)
145 > 3      # => true (greater than)
155 < 3      # => false (less than)
165 >= 5     # => true (greater or equal)
175 <= 5     # => true (less or equal)
18
19# Logical operators
20true && false  # => false (and)
21true || false  # => true (or)
22!true          # => false (not)

1# Symbols start with a colon
2status = :active
3role = :admin
4
5# Symbols are commonly used as hash keys
6user = {
7  name: "John",      # Same as :name => "John"
8  email: "john@example.com",
9  role: :admin
10}
11
12# Comparing symbols is faster than strings
13:active == :active  # => true (comparing object IDs)
14"active" == "active" # => true (comparing characters)
15
16# Converting between symbols and strings
17:hello.to_s   # => "hello"
18"hello".to_sym # => :hello

1# Creating arrays
2numbers = [1, 2, 3, 4, 5]
3names = ["Alice", "Bob", "Charlie"]
4mixed = [1, "two", :three, 4.0]
5
6# Shorthand for string arrays
7fruits = %w[apple banana cherry]  # => ["apple", "banana", "cherry"]
8
9# Accessing elements
10numbers[0]     # => 1 (first element)
11numbers[-1]    # => 5 (last element)
12numbers[1..3]  # => [2, 3, 4] (range)
13numbers.first  # => 1
14numbers.last   # => 5
15
16# Modifying arrays
17numbers << 6          # Add to end: [1, 2, 3, 4, 5, 6]
18numbers.push(7)       # Same: [1, 2, 3, 4, 5, 6, 7]
19numbers.unshift(0)    # Add to front: [0, 1, 2, 3, 4, 5, 6, 7]
20numbers.pop           # Remove last: returns 7
21numbers.shift         # Remove first: returns 0
22
23# Useful array methods
24[1, 2, 3].length      # => 3
25[1, 2, 3].empty?      # => false
26[1, 2, 2, 3].uniq     # => [1, 2, 3]
27[3, 1, 2].sort        # => [1, 2, 3]
28[1, 2, 3].reverse     # => [3, 2, 1]
29[1, 2, 3].include?(2) # => true
30[1, 2, 3].join(", ")  # => "1, 2, 3"

1# Creating hashes
2user = {
3  name: "John",
4  age: 30,
5  email: "john@example.com"
6}
7
8# Old syntax (still valid)
9user = { :name => "John", :age => 30 }
10
11# Accessing values
12user[:name]    # => "John"
13user[:age]     # => 30
14user[:missing] # => nil
15
16# With default value
17scores = Hash.new(0)
18scores[:player1] += 10  # Works without error
19
20# Modifying hashes
21user[:city] = "New York"  # Add new key
22user[:age] = 31           # Update existing key
23user.delete(:email)       # Remove a key
24
25# Useful hash methods
26user.keys       # => [:name, :age, :city]
27user.values     # => ["John", 31, "New York"]
28user.key?(:name) # => true
29user.value?("John") # => true
30user.merge({ country: "USA" }) # Combine hashes

1value = nil
2
3# Checking for nil
4value.nil?     # => true
5value == nil   # => true (but .nil? is preferred)
6
7# Safe navigation operator (Ruby 2.3+)
8user = nil
9user&.name  # => nil (no error)
10
11# Default values
12name = nil
13name || "Anonymous"  # => "Anonymous"
14
15# Dig method for nested hashes
16data = { user: { profile: { name: "John" } } }
17data.dig(:user, :profile, :name)  # => "John"
18data.dig(:user, :settings, :theme) # => nil (no error)

1# To String
242.to_s           # => "42"
33.14.to_s         # => "3.14"
4:symbol.to_s      # => "symbol"
5[1, 2, 3].to_s    # => "[1, 2, 3]"
6
7# To Integer
8"42".to_i         # => 42
9"3.14".to_i       # => 3
10"hello".to_i      # => 0
11
12# To Float
13"3.14".to_f       # => 3.14
1442.to_f           # => 42.0
15
16# To Symbol
17"hello".to_sym    # => :hello
18
19# To Array
20(1..5).to_a       # => [1, 2, 3, 4, 5]
21{ a: 1 }.to_a     # => [[:a, 1]]