Airport 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:
User Stories
As an air traffic controller
So planes can land safely at my airport
I would like to instruct a plane to land
As an air traffic controller
So planes can take off safely from my airport
I would like to instruct a plane to take off
As an air traffic controller
So that I can avoid collisions
I want to prevent airplanes landing when my airport if full
As an air traffic controller
So that I can avoid accidents
I want to prevent airplanes landing or taking off when the weather is stormy
As an air traffic controller
So that I can ensure safe take off procedures
I want planes only to take off from the airport they are at
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
As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a flying plane cannot take off and cannot be in an airport
As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a plane that is not flying cannot land and must be in an airport
As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a plane that has taken off from an airport is no longer in that airport
Here are the user stories converted into a Domain Model:
| Object | Messages | Object | Messages | Object | Messages |
|---|---|---|---|---|---|
| airport | land | plane | land | weather | stormy? |
| take_off | take_off | ||||
| airport |
Approach
My approach to solving this challenge was to start with an Airport class, build it as much as I could until I needed to start understanding how one class object would interact with another one. At some point I found it's better to extract the weather behaviour into a separate class, with this class containing a single method #stormy? which returned true with a probability of 5%. It has been implemented with the Kernel method rand.
Installation
Clone the repository:
$ git clone git@github.com:yevdyko/airport-challenge.git
Change into the directory:
$ cd airport-challenge
If you don't have bundle already, run the command:
$ gem install bundle
Install all dependencies with:
$ bundle
Testing
To run the tests:
$ rspec
How to use
To see the code in action, open IRB and require the files:
2.3.0 :001 > require './lib/weather'
=> true
2.3.0 :002 > require './lib/plane'
=> true
2.3.0 :003 > require './lib/airport'
=> true
Create a weather object:
2.3.0 :004 > weather = Weather.new
=> #<Weather:0x007f94420bb430>
Create a new airport:
2.3.0 :005 > airport = Airport.new(weather)
=> #<Airport:0x007f94420b22b8 @weather=#<Weather:0x007f94420bb430>,
@capacity=25, @planes=[]>
Create some planes:
2.3.0 :006 > plane1 = Plane.new
=> #<Plane:0x007f94420aa1d0 @flying=true>
2.3.0 :007 > plane2 = Plane.new
=> #<Plane:0x007f94420a02c0 @flying=true>
Land planes:
2.3.0 :008 > airport.land(plane1)
=> [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
@weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]
2.3.0 :009 > airport.land(plane2)
=> [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
@weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>,
#<Plane:0x007f94420a02c0 @flying=false, @airport=#<Airport:0x007f94420b22b8
@weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]
If the weather is stormy, you may need to try landing the plane a few times.
Send a plane to take off:
2.3.0 :010 > airport.take_off(plane2)
=> #<Plane:0x007f94420a02c0 @flying=false, @airport=#<Airport:0x007f94420b22b8
@weather=#<Weather:0x007f94420bb430>, @capacity=25,
@planes=[#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8 ...>>,
#<Plane:0x007f9442098890 @flying=false, @airport=#<Airport:0x007f94420b22b8 ...>>]>>
Check the planes in the airport:
2.3.0 :011 > airport.planes
=> [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
@weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]