Output display as null (Ruby)

Question

Here when we print array elements it display null value all time like "[nil, nil, nil, nil]" Values are not getting stored in array.

class Flight
  def initilize(flight_id, flight_num, flight_orgin, flight_destination)
    @id= flight_id
    @number = flight_number
    @origin = flight_origin
    @destination = flight_destination
  end

  def read_flight()
    puts "enter flight id"
    flight_id = gets.chomp
    puts "enter flight number"
    flight_number = gets.chomp
    puts "enter flight origin location"
    flight_origin = gets.chomp
    puts "enter destination"
    flight_destination = gets.chomp
  end
  def print_flight(id, number, orgin, destination)
    puts "_____Flight details______"
    puts "Flight_id         :#{id}"
    puts "Flight_number     :#{number}"
    puts "Flight_orgin      :#{orgin}"
    puts "Flight_destination:#{destination}"
  end
  def read_flights(id, number, orgin, destination)
    puts "_______Array of flights______"
    flightid = Array.new
    flightid.push(id, number, orgin, destination)
    puts "#{flightid}"
  end
end
input_flight = Flight.new
input_flight.read_flight
input_flight.print_flight(@id, @num, @orgin, @destination)
input_flight.read_flights(@id, @num, @orgin, @destination)

Without using a class or instance variable we want to do it

User input

enter flight id

2

enter flight number

2342

enter flight origin location

cochin

enter destination

tvm

output

Flight details_

Flight_id :

Flight_number :

Flight_orgin :

Flight_destination:

_Array of flights

[nil, nil, nil, nil]

Answer 1

Here is my version of adjustion:

class Flight
  attr_reader :id, :number, :origin, :destination

  def read_flight
    puts "enter flight id"
    @id = gets.chomp
    puts "enter flight number"
    @number = gets.chomp
    puts "enter flight origin location"
    @origin = gets.chomp
    puts "enter destination"
    @destination = gets.chomp
  end

  def print_flight
    puts "_____Flight details______"
    puts "Flight_id         :#{id}"
    puts "Flight_number     :#{number}"
    puts "Flight_orgin      :#{origin}"
    puts "Flight_destination:#{destination}"
  end

  def read_flights
    puts "_______Array of flights______"
    flightid = [id, number, origin, destination]
    puts "#{flightid}"
  end
end
input_flight = Flight.new
input_flight.read_flight
input_flight.print_flight
input_flight.read_flights

Explanation:

Each instance of ruby class can have as many instance variables (which begin with @) as possible. Those instance variables live in an instance so they keep their value across the methods.

So you should assign the value you want to instance variables, for example:

@id = gets.chomp

then use it in another method:

def print_flight
    puts "_____Flight details______"
    puts "Flight_id         :#{@id}"
end

However, add @ everytime we want to use the instance variables is pretty tedious. That's why attr_reader comes in. When you write attr_reader:

attr_reader :id, :number, :origin, :destination 

You actually declare 4 methods inside Flight:

def id
  @id
end

def number
  @number
end

def origin
  @origin
end

def destination 
  @destination 
end

Then you can just use id, number, origin, destination without the leading @`