Output display as null (Ruby) - arrays

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

The #id, #num, #orgin, #destination parameters will be nil if you don't set them anywhere.
So when you make these two calls:
input_flight.print_flight(#id, #num, #orgin, #destination)
input_flight.read_flights(#id, #num, #orgin, #destination)
You basically just send nils into the function:
input_flight.print_flight(nil, nil, nil, nil)
input_flight.read_flights(nil, nil, nil, nil)
If you want to access the variables read from the input:
First, you need to store them somewhere. For ex: store them inside the instance variables when read_flight function is called.
Then, refer the instance variable when you want to push values in the array.
Ex:
def read_flight
puts "enter flight id"
#id = gets.chomp # store inside instance variable
puts "enter flight number"
#number = gets.chomp
puts "enter flight origin location"
#origin = gets.chomp
puts "enter destination"
#destination = gets.chomp
end
def read_flights
...
flightid.push(#id, #number, #origin, #destination) # access instance variables here
...
end
You can learn more about Ruby's variable scoping (instance variables, global variables, etc) here: https://www.techotopia.com/index.php/Ruby_Variable_Scope

Answer 2

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 #`

Answer 3

You're initializing with nil values in your constructor (def initialize), to fix that you can pass the values to the .new or change the read_flight as follows:
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
This will modify the class-scoped variables.
Or alternatively you can have default values in the constructor (not recommended) using the || operator:
def initilize(flight_id, flight_num, flight_orgin, flight_destination)
#id= flight_id || 0
#number = flight_number || 0
#origin = flight_origin || ""
#destination = flight_destination || ""
end

Answer 4

First of all, be careful, because you did a lot of little but important mistakes. It's ok, we all started like that)
For example, your 'initialize' method name is not correct!
Your: 'initilize'
Correct: 'initialize'
It's important to name default methods correct.
Also, when you initialize variables with method arguments:
def initilize(flight_id, flight_num, flight_orgin, flight_destination)
#id= flight_id
#number = flight_num #you have to name it just like argument in method not flight_number, because it does not exist at all
#origin = flight_origin #same here, you forgot one letter
#destination = flight_destination
end
If you want user to initialize your instances then don't initialize them by yourself, delete arguments in initialize method.
Also, you can use instance variables in entire class, it's really helpful!
So, i corrected a little:
class Flight
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.to_s
puts "Flight_number : " + #number.to_s
puts "Flight_origin : " + #origin
puts "Flight_destination: " + #destination
end
def read_flights
puts "_______Array of flights______"
flightid = Array.new
flightid.push({ #id,#number,#origin,#destination })
puts "#{flightid}"
end
end
Check:
input_flight = Flight.new
input_flight.read_flight
input_flight.print_flight
input_flight.read_flights