Intro to OOP
Intro to OOP
Warmup
- Write down to classes of things (e.g. Classroom) and for each write down two instances of that class (e.g.
bem1_classroom) - For each class of thing, write down some attributes that might distinguish one instance from another (e.g.
tables,chairs,length,width,height,pairing_stations)
Setting Default Values
# classroom.rb
class Classroom
# attr_readers
def initialize(length, width, height = 20)
@length = length
@width = width
@height = height
end
# ... other methods
end
Using Default Values
# classroom_runner.rb
standard_room = Classroom.new(15, 15)
short_room = Classroom.new(15, 15, 10)
puts "Standard Height: #{standard_room.height}"
puts "Short Height: #{short_room.height}"
Setting Initial State Without Parameters
# classroom.rb
class Classroom
# ... attr_readers
def initialize(length, width, height = 20)
@length = length
@width = width
@height = height
@students = []
end
# ... other methods
end
Adding to Our @students Array
# classroom.rb
class Classroom
attr_accessor :length,
:width,
:height,
:students
# ... initialize, area, volume, add_length
def add_student(student)
@students << student
end
end
Creating a Student Class
# student.rb
class Student
def initialize(name)
@name = name
end
end
Passing Objects to Other Objects
# classroom_runner.rb
require './classroom'
require './student'
classroom_a = Classroom.new(10, 5, 20)
sal = Student.new("Sal")
ali = Student.new("Ali")
classroom_a.add_student(sal)
classroom_a.add_student(ali)
puts classroom_a.students
Using Objects in Other Objects
# classroom.rb
class Classroom
# attr_accessors, previously defined methods
def print_roster
@students.each do |student|
puts student.name
end
end
end
Summary
- What are some examples of classes and instances from everyday life?
- How would you define a
Personclass that had height, weight, and age attributes in Ruby? - What are the two main responsibilities of an instance of an object in Ruby?
Video
This is a 5 minute explanation of Object Oriented Programming. It’s geared towards JavaScript developers, and they use the term “Object” where you should use “Instance”, but otherwise, it does a good job of explaining the philosophy of OOP
