- A Different Kind of Duck Typing
- The Template Method Strikes Again
- Parameterized Factory Methods
- Classes Are Just Objects, Too
- Bad News: Your Program Hits the Big Time
- Bundles of Object Creation
- Classes Are Just Objects (Again)
- Leveraging the Name
- Using and Abusing the Factory Patterns
- Factory Patterns in the Wild
- Wrapping Up
This chapter is from the book
This chapter is from the book
This chapter is from the book
Bad News: Your Program Hits the Big Time
Suppose even more success has befallen your pond simulator, and new requirements are pouring in faster than ever. The most pressing request is to extend this program to model other types of habitats besides ponds. In fact, a jungle simulation seems to be the next order of business.
Clearly, this change calls for major surgery on the code. You obviously will need classes for the jungle animals (perhaps tigers) and the jungle plants (mainly trees):
class Tree
def initialize(name)
@name = name
end
def grow
puts("The tree #{@name} grows tall")
end
end
class Tiger
def initialize(name)
@name = name
end
def eat
puts("Tiger #{@name} eats anything it wants.")
end
def speak
puts("Tiger #{@name} Roars!")
end
def sleep
puts("Tiger #{@name} sleeps anywhere it wants.")
end
end
You also need to change your Pond class’s name to something more appropriate for jungles as well as ponds. Habitat seems like a good choice:
jungle = Habitat.new(1, Tiger, 4, Tree) jungle.simulate_one_day pond = Habitat.new( 2, Duck, 4, WaterLily) pond.simulate_one_day
Other than the name change, Habitat is exactly the same as our last Pond implementation (the one with the plant and animal classes). We can create new habitats in exactly the same way that we did ponds.