ruby_oop/index.html at gh-pages · denysxftr/ruby_oop · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <title>OOP</title>
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class: center, middle

# OOP in RUBY

---

# Defining a simple class

```ruby
  class Car
    # code...
  end

  AnotherCar = Class.new do
    # code...
  end
```
???
класс это тоже класс

---

# Creating objects

```ruby
car = Car.new

car.class # => Car

car.is_a? Car # => true

Car.ancestors
# => [Car, Object, Kernel, BasicObject]

```
???
откуда у экземпляра пустого класса появились методы?
___
даже пустой класс наследуется от базовых классов которые предоставляют базовые методы

---

# Defining methods
```ruby
  class Car
    def accelerate!
      @moving = true
    end

    def stop!
      @moving = false
    end

    def moving?
      @moving
    end
  end
```
---

# Defining methods

```ruby
  car = Car.new   # => #<Car:0x00000002033700>
  car.moving?     # => nil
  car.accelerate! # => true
  car.moving?     # => true
  car.stop!       # => false
  car.moving?     # => false

  car.inspect
  # => "#<Car:0x00000002033700 @moving=false>"
```
???
inspect - один из стандартных методов (строкое представление обьекта)
___
показывает состояние обьекта
---
# Initializers
```ruby
  class Car
    def initialize(type)
     @type = type
    end

    def big?
      @type == 'big'
    end
  end

  car = Car.new('big')

  car.big? # => true
```
???
почему мы вызываем new, а определяем initialize?


---
# Attributes
```ruby
  class Snake
    def length
      @meters * 100
    end

    def length=(santimeters)
      @meters = santimeters / 100.0
    end
  end

  snake = Snake.new
  snake.length = 150 # => 150
  snake.length       # => 150.0
  snake.inspect
  #=> "#<Snake:0x00000002777930 @meters=1.5>"
```
---
# Attributes
## attr_accessor
```ruby
class Snake
  def length
    @length
  end

  def length=(new_value)
    @length = new_value
  end
end

class Snake
  attr_accessor :length
end
```
---
# Attributes
## attr_reader
```ruby
class Snake
  def length
    @length
  end
end

class Snake
  attr_reader :length
end
```
---
# Attributes
## attr_writer
```ruby
class Snake
  def length=(new_value)
    @length = new_value
  end
end

class Snake
  attr_writer :length
end
```
---
# Attributes
## drawing the line
```ruby
class Snake
  def length # attr_reader, attr_accessor
    @length
  end

  def length=(new_value) # attr_writer, attr_accessor
    @length = new_value
  end
end
```
---
# Defining operators
```ruby
  class Snake
    attr_reader :length

    def initialize(length)
      @length = length
    end

    def +(other)
      Snake.new(length + other.length)
    end
  end
```
```ruby
snake_1 = Snake.new(1) # => #<Snake:0x00000002f7d878 @length=1>
snake_2 = Snake.new(2) # => #<Snake:0x00000002f09fe0 @length=2>
snake_3 = snake_1 + snake_2
# => #<Snake:0x00000002eb3050 @length=3>
```
???
Было бы неплохо еще проверить класс
---
# Comparation
```ruby
  class Snake
    attr_reader :length

    def initialize(length)
      @length = length
    end
  end

  snake = Snake.new(1) # => #<Snake:0x000000020800c8 @length=1>
  other_snake = Snake.new(1) # => #<Snake:0x00000001e80ae8 @length=1>
  snake == other_snake # => false
```
???
айдишник же разный вот и разные обьeкты
___
цифры тоже обьекты.. как они сравниваются?
___
показать object_id цифр
---
# Comparation
```ruby
  class Snake
    attr_reader :length

    def initialize(length)
      @length = length
    end

    def ==(other)
      if other.is_a? Snake
        length == other.length
      else
        false
      end
    end
  end

  snake = Snake.new(1)
  other_snake = Snake.new(1)
  snake == other_snake # => true
```
---
# Self
```ruby
  class Snake
    attr_reader :length

    def initialize
      @length = 1
    end

    def snake
      self
    end

    def length_redefign
      length # => 1
      length = 5
      length # => 5
      self.length # => 1
    end
  end
```
???
просто аналог this
---
# Class methods
```ruby
  class Snake
    def self.description
      'SNAAAAKESSS'
    end
  end

  class Snake
    class << self
      def normal_description
        'Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes' \
        'that can be distinguished from legless lizards by their lack of eyelids and external ears.'
      end
    end
  end

  Snake.description # => 'SNAAAAKESSS'
  Snake.normal_description # => 'Snakes ...'
```
???
просто разный синтаксис. self тут Snake
___
но если что class << пишет в синглтон класс класса (слайд с рисуночком)
---
# Class variables
```ruby
  class Snake
    @@count = 0

    def initialize
      @@count += 1
    end

    def all_count
      @@count
    end
  end
  Snake.new.all_count # => 1
  Snake.new.all_count # => 2
```
???
статическая переменная и инстансы имеют к ней доступ
---
# Class instance variables
```ruby
  class Snake
    @count = 0
    def self.add
      @count += 1
    end
    def initialize
      self.class.add
    end
    def all_count
      @count
    end
    def self.count
      @count
    end
  end
  snake = Snake.new
  # Oops..
  snake.all_count # => nil
  Snake.count # => 1
```
???
а это переменная имено класса как обьекта. она его. и инстансы ее не видят
---
# Class constants
```ruby
  class Snake
    NORMAL_LENGTH = 2
  end

  Snake::NORMAL_LENGTH # => 2

  Snake::NORMAL_COLOR = '#6B554A'
  Snake::NORMAL_COLOR # => '#6B554A'

  Snake::NORMAL_COLOR = '#2D2D2D' # => warning: already initialized constant Snake::NORMAL_COLOR
  Snake::NORMAL_COLOR # => '#2D2D2D'
```
---
# Visibility private
```ruby
  class Snake
    attr_reader :length

    private

    def initialize
      set_defaults
    end

    def set_defaults
      @length = 2
    end
  end

  snake = Snake.new
  snake.length # => 2
  snake.set_defaults
  # NoMethodError: private method `set_defaults'
  # called for #<Snake:0x00000001d29b90 @length=2>
```
???
ну да initialize приватный.. он же вызывается другим методом так что всё ок
---
# Visibility protected
```ruby
  class Snake
    def +(other)
      Snake.new(length + other.length)
    end

    private

    def initialize(length)
      @length = length
    end

    protected

    attr_reader :length
  end
```
---
# Protected example
```ruby
  snake1 = Snake.new(1)
  snake2 = Snake.new(2)

  snake1 + snake2 # => #<Snake:0x00000001e82d70 @length=3>

  snake1.length
  # NoMethodError: protected method `length'
  # called for #<Snake:0x00000001f95028 @length=1>

```

---
# Inheritance

```ruby
class Snake
  attr_reader :length
  def initialize(length)
    @length = length
  end
end

class LazySnake < Snake
  def initialize(length)
    @sleeping = false
    super
  end
  def toggle_sleep
    @sleeping = !@sleeping
  end
  def sleeping?
    @sleeping
  end
end
```
???
множественого наследования нет
___
есть миксины
---
# Inheritance example
```ruby
lazy = LazySnake.new(2)
lazy.length # => 2
lazy.sleeping? # => false
lazy.toggle_sleep
lazy.sleeping? # => true
```
---
# Inheritance
## super
```ruby
class LazySnake < Snake
  def initialize(length)
    super(length + 1)
  end
end

lazy = LazySnake.new(2)
lazy.length # => 3
```
???
по умалчанию супер свхатит теже аргументы что и метод где он дергается
___
но можно указать другие аргументы
---
# Inheritance
## class variables
```ruby
class A
  @@value = 1
  def self.value
    @@value
  end
end
A.value # => 1

class B < A
  @@value = 2
end

class C < A
  @@value = 3
end

B.value # => 3
```
???
расшареная
---
# Inheritance
## constants
```ruby
class A
  NUM = 2
end

class B < A
end

A::NUM # => 2
B::NUM # => 2

B::NUM = 3

A::NUM # => 2
B::NUM # => 3
```
???
а константы везде свои
---
# Singleton methods
```ruby
class Snake
  def Snake.count
  end
end

class Snake
  class << self
    def count
    end
  end
end

class << Snake
  def count
  end
end
```
???
same and eigenclass
---
# Custom behaviour of instance
```ruby
snake = Snake.new
def snake.name
  "John"
end
snake.name # => John

class << snake
  def name
    "David"
  end
end
snake.name # => David

another = Snake.new
another.name # => NoMethodError: undefined method 'name'
```
???
class << snake - это запись в eigenclass
___
обьекты в руби не хранят методы, методы хранятся в другом месте
___
обьекты хранят состояние. inspect тому пример
---
# Module
```ruby
module Speaking
  def hi
    puts 'HI!!!'
  end
end

class Snake
  include Speaking
end

snake = Snake.new
snake.hi
# 'HI!!!!'
```
???
комната в которой куча хлама
___
разкладываем хлам по коробочкам (модулям)
---

# Module constants
```ruby
module M
  class C
    X = 'a constant'
  end
  C::X  # => "a constant"
end
M::C::X # => "a constant"

module M
  Y = 'another constant'
  class C
    ::M::Y # => "another constant"
  end
end

M.constants # => [:C, :Y]
```
---
class: small

# Constants lookup order
```ruby
module Kernel
  A = B = C = D = E = F = "from kernel"
end

A = B = C = D = E = "from toplevel"

class Super
  A = B = C = D = "from superclass"
end

module Included
  A = B = C = "from included module"
end

module Enclosing
  A = B = "from enclosing module"

  class Local < Super
    include Included

    A = "defined locally"

    puts A  # "defined locally"
    puts B  # "from enclosing module"
    puts C  # "from included module"
    puts D  # "from superclass"
    puts E  # "from toplevel"
    puts F  # "from kernel"
  end
end
```
---
# Include and extend
```ruby
module A
  def a
    puts 'a'
  end
end

module B
  def b
    puts 'b'
  end
end
```
???
два простых модуля для обьяснения
___
и вобще в модули можно всунуть все что угодно
---
# Include and extend
```ruby
class Test
  include A
  extend B
end

test = Test.new
test.a # 'a'

test.b # NoMethodError
Test.b # 'b'

test.extend(B)
test.b # 'b'
```
???
include -добавляет содержимое модуля для инстансов которые будут сделаны
___
exntend - добавляет содержимое для текущего обьекта
---
# Include and extend and method lookup
![Lookup](img/lookup.png)
---
# Exceptions
```ruby
begin
  puts 'I am before the raise.'
  raise 'An error has occured.'
  puts 'I am after the raise.'
rescue
  puts 'I am rescued.'
end
puts 'I am after the begin block.'
```
```
I am before the raise.
I am rescued.
I am after the begin block.
```

---
# Exceptions ensure
```ruby
begin
  raise "A test exception."
rescue Exception => e
  puts e.message
  puts e.backtrace.inspect
ensure
  puts "Ensuring execution"
end

A test exception.
# ["test.rb:2:in '<main>'"]
# Ensuring execution
```
???
ensure - всегда вызывается
___
пример - закрыть файл
---
# Exceptions else
```ruby
begin
  puts "A test exception."
rescue Exception => e
  puts e.message
  puts e.backtrace.inspect
else
  puts "Executes if there is no exception"
ensure
  puts "Ensuring execution"
end
# A test exception.
# Executes if there is no exception
# Ensuring execution
```
???
else - если нет исключения
___
пример - вывод радосного сообщения
---
# Throw and catch
```ruby
def try(number)
  throw :two! if number == 2
  puts number
end

catch :two! do
  try(1)
  try(2)
  try(3)
end

try(4)

# 1
# 4
```
???
вылезти из глубокой вложености

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