Ruby Variable and Data Type Quiz

def example_method
  local_var = 'Hello'
  puts local_var
end

example_method
puts local_var

$global_var = 'I am global'

def test_method
  puts $global_var
end

test_method

class Person
  def initialize(name)
    @name = name  # instance variable
    local_var = 'temporary'  # local variable
  end
  
  def display
    puts @name
    puts local_var  # This will cause an error
  end
end

class Vehicle
  @@vehicle_count = 0  # class variable
  
  def initialize
    @@vehicle_count += 1
  end
  
  def self.total_vehicles
    @@vehicle_count
  end
end

name_symbol = :name
name_string = 'name'

puts name_symbol.object_id  # Same object each time
puts :name.object_id       # Same object
puts 'name'.object_id      # Different object each time
puts 'name'.object_id      # Different object

integer_num = 42        # Integer
float_num = 42.0        # Float

puts integer_num.class   # Integer
puts float_num.class     # Float

age = 25
is_adult = age >= 18

if is_adult
  puts 'You are an adult'
else
  puts 'You are not an adult'
end

PI = 3.14159
MAX_USERS = 100

class Circle
  RADIUS = 5
end

puts PI
puts Circle::RADIUS

def check_variable
  if defined? local_var
    puts 'local_var is defined'
  else
    puts 'local_var is not defined'
  end
end

check_variable

name = 'Alice'
age = 30
message = "Hello, my name is #{name} and I am #{age} years old."
puts message

class Animal
  def initialize(name)
    @name = name
  end
end

class Dog < Animal
  def initialize(name, breed)
    super(name)
    @breed = breed
  end
  
  def info
    puts "#{@name} is a #{@breed}"
  end
end

result = nil

if result
  puts 'Result exists'
else
  puts 'Result is nil or false'
end

class Example
  @@class_var = 'shared'  # class variable
  @instance_var = 'per class'  # class instance variable
  
  def self.show_vars
    puts @@class_var
    puts @instance_var
  end
end

symbols = [:name, :age, :email] * 1000  # Same objects reused
strings = ['name', 'age', 'email'] * 1000  # New objects each time

puts symbols.uniq.size  # 3 unique symbols
puts strings.uniq.size  # Still 3000 strings

puts undefined_variable

result1 = true && 'hello'    # returns 'hello'
result2 = false && 'hello'   # returns false
result3 = 'hello' || 'world'  # returns 'hello'
result4 = nil || 'default'    # returns 'default'

message = 'outer'

def display_message
  message = 'inner'  # This shadows the outer variable
  puts message
end

display_message
puts message

class Parent
  CONSTANT = 'parent'
end

class Child < Parent
  CONSTANT = 'child'  # Creates new constant
end

puts Parent::CONSTANT
puts Child::CONSTANT

puts 1 == 1.0    # true (value equality)
puts 1 === 1.0   # true (value equality for numbers)

puts String === 'hello'  # true (class membership)
puts (1..10) === 5       # true (range membership)

$global_counter = 0

def increment
  $global_counter += 1
end

def reset
  $global_counter = 0
end

def process_data(data)
  puts data.upcase  # Works if data responds to upcase
end

process_data('string')  # Works
process_data(:symbol)    # Error - Symbol doesn't have upcase

class Person
  def initialize(name)
    @name = name
  end
  
  def name
    @name  # nil if not initialized
  end
end

person = Person.new('Alice')
puts person.name

variable = 'string'
variable = 42
variable = [1, 2, 3]

puts variable.class  # Changes based on assignment

module MathConstants
  PI = 3.14159
  E = 2.71828
end

puts MathConstants::PI

integer = 1
float = 1.0

puts integer == float    # true
puts integer.eql?(float) # false
puts integer.equal?(float) # false

class Parent
  @@count = 0
end

class Child < Parent
  @@count = 1  # Affects all classes in hierarchy
end

puts Parent.class_variable_get(:@@count)  # 1
puts Child.class_variable_get(:@@count)   # 1

hash_with_symbols = { name: 'Alice', age: 30 }
hash_with_strings = { 'name' => 'Alice', 'age' => 30 }

# Symbol keys are faster to compare and use less memory

result = find_user('nonexistent')

if result
  puts 'User found'
else
  puts 'User not found'  # This executes
end

def process(data)
  # No type checking - accepts any object
  data.upcase  # May fail if data doesn't respond to upcase
end

module DatabaseConfig
  HOST = 'localhost'
  PORT = 5432
end

class UserRepository
  include DatabaseConfig
  
  def connect
    # Can access HOST and PORT
  end
end

result = expensive_operation? && another_expensive_operation?
# Short-circuits if first operation returns false

class BankAccount
  def initialize(balance)
    @balance = balance  # Encapsulated state
  end
  
  def deposit(amount)
    @balance += amount
  end
  
  def balance
    @balance  # Controlled access
  end
end

def process_list(items)
  if items  # Works for both nil and empty arrays
    items.each { |item| puts item }
  end
end

class DynamicClass
  [:name, :age, :email].each do |attr|
    define_method(attr) { instance_variable_get("@#{attr}") }
    define_method("#{attr}=") { |value| instance_variable_set("@#{attr}", value) }
  end
end