This is my attempt at the Makers Academy Week #1 weekend challenge.
We have a request from a client to write the software to control the flow of planes at an airport. The planes can land and take off provided that the weather is sunny. Occasionally it may be stormy, in which case no planes can land or take off. Here are the user stories that we worked out in collaboration with the client:
As an air traffic controller
So I can get passengers to a destination
I want to instruct a plane to land at an airport
As an air traffic controller
So I can get passengers on the way to their destination
I want to instruct a plane to take off from an airport and confirm that it is no longer in the airport
As an air traffic controller
To ensure safety
I want to prevent takeoff when weather is stormy
As an air traffic controller
To ensure safety
I want to prevent landing when weather is stormy
As an air traffic controller
To ensure safety
I want to prevent landing when the airport is full
As the system designer
So that the software can be used for many different airports
I would like a default airport capacity that can be overridden as appropriate
I tackled this challenge by assuming that the Airport, Plane, and Weather would all be treated as separate units.
I ascertained from the user that the plane would be receiving the messages to land, rather than the airport. Therefore, the bulk of the code for this project is contained in the Plane class and its associated tests in plane_spec.
The weather is determined using the rand function that returns a float anywhere between 0 and 1. I set the storm chance to a constant of 0.05, meaning that the stormy? method would return true roughly 1 in 20 (or 0.05 in 1) times.
The land and take_off methods inside the Plane class take 2 arguments: the airport to land in, and the weather object. I believe that this approach most accurately follows the user stories, and most accurately represents its real-life counterpart. When a plane is instructed to land, landing_checks and take_off_checks are executed with the same 2 arguments to account for edge cases relating to the current airport and current weather.
Each plane object has a location attribute that defaults to the sky, and when the plane lands is assigned to the current airport object. This protects against an edge case where a plane is asked to land in an airport, when it is already in a different airport.
Currently, improvements could be made relating to the attr_reader landed_planes. This should not be publicly readable, but for testing purposes and methods inside other classes, I have had to leave it in this state. Given more time, I would refactor my code to have this attribute as private.
Here is a full story of how my app can be used inside irb:
$ irb
2.5.0 :004 > airport = Airport.new
=> #<Airport:0x00007fee9806e5d0 @landed_planes=[], @capacity=20>
2.5.0 :005 > airport_2 = Airport.new(1)
=> #<Airport:0x00007fee9805d488 @landed_planes=[], @capacity=1>
2.5.0 :006 > plane = Plane.new
=> #<Plane:0x00007fee988cef90 @location=:sky>
2.5.0 :007 > plane_2 = Plane.new
=> #<Plane:0x00007fee988b59a0 @location=:sky>
2.5.0 :008 > weather = Weather.new
=> #<Weather:0x00007fee98865f18>
2.5.0 :009 > plane.land(airport, weather)
=> #<Airport:0x00007fee9806e5d0 @landed_planes=[#<Plane:0x00007fee988cef90 @location=#<Airport:0x00007fee9806e5d0 ...>>], @capacity=20>
2.5.0 :010 > plane_2.land(airport, weather)
=> #<Airport:0x00007fee9806e5d0 @landed_planes=[#<Plane:0x00007fee988cef90 @location=#<Airport:0x00007fee9806e5d0 ...>>, #<Plane:0x00007fee988b59a0 @location=#<Airport:0x00007fee9806e5d0 ...>>], @capacity=20>
2.5.0 :011 > airport.hangar_report
=> "Planes currently in the hangar: #<Plane:0x00007fee988cef90>, #<Plane:0x00007fee988b59a0>"
2.5.0 :012 > plane.take_off(airport, weather)
=> :sky
2.5.0 :013 > plane_2.take_off(airport, weather)
=> :sky
2.5.0 :014 > plane.land(airport_2, weather)
=> #<Airport:0x00007fee9805d488 @landed_planes=[#<Plane:0x00007fee988cef90 @location=#<Airport:0x00007fee9805d488 ...>>], @capacity=1>
2.5.0 :015 > plane_2.land(airport_2, weather)
Traceback (most recent call last):
4: from /Users/Joel/.rvm/rubies/ruby-2.5.0/bin/irb:11:in `<main>`
3: from (irb):15
2: from /Users/Joel/Makers/week1/airport_challenge/lib/plane.rb:9:in `land`
1: from /Users/Joel/Makers/week1/airport_challenge/lib/plane.rb:23:in `landing_checks`
RuntimeError (Airport is full!)
2.5.0 :016 > plane.location
=> #<Airport:0x00007fee9805d488 @landed_planes=[#<Plane:0x00007fee988cef90 @location=#<Airport:0x00007fee9805d488 ...>>], @capacity=1>
2.5.0 :017 > plane.location == airport
=> false
2.5.0 :018 > plane.location == airport_2
=> true
2.5.0 :019 > plane.take_off(airport_2, weather)
=> :sky
2.5.0 :020 > exit
Run irb in the terminal in order to use the app. Run rspec inside the project directory to test the app.