# adapter.rb
# Converst the interface of a class into another intrerface clients expect.
# Lets classes work together that couldn't otherwise because of incompatible interfaces.
# 1. existing layout
class ClientItem
def some_operation
end
end
class MyClientItem < ClientItem
def some_operation
puts "some operation"
end
end
class Client
def process(item)
item.some_operation
end
end
# 2. class that creates conflict (adaptee): we cannot pass type in client's process() method.
class OtherItem # adaptee
def other_operation
puts "other operation"
end
end
# 3. adaptation
class ClientItemAdapter < ClientItem # adapter
def initialize
@other_item = OtherItem.new
end
# actual adaptation
def some_operation
@other_item.other_operation
end
end
# 4. test
client = Client.new
client.process(MyClientItem.new) # OK
# client.process(OtherItem.new) # OtherItem does not conform CientItem protocol
client.process(ClientItemAdapter.new) # OtherItem is adapted to CientItem protocol through adapter
other_item = OtherItem.new
class << other_item
def some_operation
puts "some operation for this instance"
end
end
client.process(other_item) # OtherItem is adapted to CientItem protocol with the help of odifying instance behavior
