How to associate instances from different classes in Ruby - ruby-on-rails

Question

I want to be able to initialize a new Car object and pass it a Person object in the parameters, so it can be saved in that Person's #cars array. Currently, I take this approach:
person = Person.new("Michael")
car = Car.new("Honda", "Accord")
person.add_car(car)
person.add_car(Car.new("Ford", "Taurus"))
person.add_car(Car.new("Toyota", "Prius"))
person.display
However, I'd like to be able to create a new car instance and pass it the Person object I want it associated with. For example:
person = Person.new("Michael")
Car.new("Honda", "Accord", person)
Car.new("Toyota", "Camry", person)
Car.new("Chevy", "Tahoe", person)
person.display
Is that even possible?
class Person
attr_accessor :name
def initialize(name)
super
#name = name
#cars = []
end
def display
puts "#{#name} has #{#cars.length} cars"
puts "----------------------------"
#cars.each do |car|
puts "#{car.make} #{car.model}"
end
end
def add_car(car)
#cars.push(car)
end
end
class Car
attr_accessor :make, :model
def initialize(make, model)
#model = model
#make = make
end
def display
puts "#{#make} #{#model}"
end
end

Answer 1

Yes, that is possible, Car#initialize can call methods on its arguments:
class Car
def initialize(make, model, person = nil)
#model = model
#make = make
person.add_car(self) if(person)
end
#...
end

Answer 2

This would be my implementation:
class Car
attr_accessor :make, :model
def initialize(make, model)
self.make = make
self.model= model
end
end
Person class
class Person
attr_accessor :name, :cars
def initialize(name, cars=[])
self.name = name
self.cars = cars || []
end
def add_car(*args)
raise ArgumentError, 'invalid arguments' if (
(args.size > 2 or args.size == 0) or
(args.size == 1 and !args[0].is_a?(Car))
)
new_car = (args.size == 2) ? Car.new(*args) : args[0]
self.cars << new_car
new_car
end
end
Now you can:
person = Person.new("Michael")
car = Car.new("Honda", "Accord")
person.add_car(car)
person.add_car("Ford", "Taurus")
person.add_car("Toyota", "Prius")
person.display
The add_car method creates a new car when make and model are passed as parameters.

Answer 3

Yes, it is possible as mu is too short's answer demonstrated, but that doesn't really make sense in my opinion. Your cars can't be used in any context without a Person, and said parameter contributes no data necessary to construct the Car object.
I would design such an API as follows:
class Person
def initialize(name)
#name = name
end
def cars
#cars ||= Array.new # Equivalent to #cars || #cars = []
end
end
person = Person.new 'Michael'
taurus = Car.new 'Ford', 'Taurus'
prius = Car.new 'Toyota', 'Prius'
person.cars << taurus << prius << Car.new('Honda', 'Accord')
This is a simpler and more direct form of KandadaBoggu's implementation that takes advantage of the Array#<< method in order to naturally associate Cars with a Person, and also doubles as an attribute reader.