trainings/CreatingReliableSoftwareCpp/Presentation/exercises/observer

Linux compilation

> mkdir build
> cd build
> cmake -DCMAKE_BUILD_TYPE=Debug ..
> make

Exercise 1

• Go into directory Core and implement Time and TimeObserver class
• Class Time should have 4 methods:
  • void attach(TimeObserver* observer); -> attach observer
  • void detach(TimeObserver* observer); -> detach observer
  • Time& operator++(); -> increment day and notify observers
  • size_t day() const; -> return current day
• Go into directory Ship and make Ship class inherit from TimeObserver
• Each time the observer will be triggered, you should give the crew food and drink
• Each crew member should consume 1 rum and 1 banana (I know they usually eat biscuits)
• If you don't have enough cargo crew should rebel
• Each day of a rebel you should subtract 5 members of the crew
• If the number of crew drops below 0, throw an exception "Game Over"

Example (We have 40 members of crew): Day: 0

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	300
Banana	200
Banana	150
----------------	----------------

DAY: 1

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	260
Banana	160
Banana	150
----------------	----------------

DAY: 2

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	220
Banana	120
Banana	150
----------------	----------------

DAY: 3

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	180
Banana	80
Banana	150
----------------	----------------

DAY: 4

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	140
Banana	40
Banana	150
----------------	----------------

DAY: 5

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	100
Banana	150
----------------	----------------

DAY: 6

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	60
Banana	110
----------------	----------------

DAY: 7

crew: 40
NAME	AMOUNT
----------------	----------------
Rum	20
Banana	70
----------------	----------------

********** Crew rebel **********

DAY: 8

crew: 35
NAME	AMOUNT
----------------	----------------
Banana	30
----------------	----------------

********** Crew rebel **********

DAY: 9

crew: 30
NAME	AMOUNT
----------------	----------------
----------------	----------------

********** Crew rebel **********

DAY: 10

crew: 25
NAME	AMOUNT
----------------	----------------
----------------	----------------

Exercise 2

• Go into directory Store and make Store class inherit from TimeObserver
• Class Store should don't know anything about class Time
• We should attach and detach observer outside of class. Think about how you can make it exception-safe (RAII)
• Each time the observer will be triggered, you should change the number of available cargo in the store
• Each time draw a number between -50 and 50 and add it to the amount of cargo
• Print everyday cargo from the Shop and verify if the amount changes

Exercise 3

• Rewrite Observer to use modern approach -> by value semantic.
• Rewrite class Ship
• Rewrite class Store
• Question: Which class was easier to rewrite?