Chain of Responsibility

1
Chain of Responsibility

• Loren Shevitz
• 28 Jan 02

2
What is it?

• Behavioral pattern
• Passes the buck
• Defecit spending

3
When to use?

• Single superclass of requests with different
  problems
• Not sure which object will eventually handle
  request
• Each request can be processed same way initially

4
Examples

• The Ubiquitous Fruit
• Lets eat! But first
• class Fruit peel()
• Consider
• Pineapple slice open with knife
• Orange fingernail.puncture()
• Grape
• In each case, dont need to know or care ahead of
  time

5
Another example

• From http//home.earthlink.net/huston2/dp/chain.h
  tml
• Coins
• Quarter, dime, nickel, penny, half-dollar, Ike
  dollar, Brass Buck all sorted.
• But only one coinslot

6
Benefits

• Eliminates need for hard-coding the relationship
  between request-maker and handler
• As with previous patterns, allows for greater
  readability and tweaking
• Another elaborate name for relatively simple
  process

7
Further discussion

• Other examples?
• Problems?
• Is 14.5 too high?