In the State Design Pattern, the same object behaves differently depending on the current state of the object.
For example, take the case of Chicken preparation.
When it is delivered, it remains in an uncleaned state. Hence the first task will be to clean it.
At that time if you call a specific method of the Chicken State, say, cook, it will behave differently (say maybe flash out a message that the chicken can't be cooked until it is properly cleaned and marinated). But the same cook method will cook the chicken once it is in the Marinated State. This time the "cook" method will properly cook the chicken and will flash out a different message - maybe like the Chicken is getting cooked - so have patience.
In the example, we have a ChickenState interface and then Mamma as the chef. The transition from one state to another is done at the end of the appropriate method of the interface at each state.
Enjoy the State Pattern written in written in Python
from abc import ABC, abstractmethod
import time
class Mamma():
def __init__(self, state):
self._state = state
def getstate(self):
return self._state
def setstate(self, state):
self._state = state
def startpreparation(self):
self._state.wash()
self._state.marinate()
self._state.cook()
self._state.serve()
class State(ABC):
@abstractmethod
def wash(self):
pass
@abstractmethod
def marinate(self):
pass
@abstractmethod
def cook(self):
pass
@abstractmethod
def serve(self):
pass
class UncleanedState(State):
def __init__(self, mamma):
self._mamma = mamma
def wash(self):
print("chicken is in the uncleaned state and is getting cleaned:next state will be cleaned state")
time.sleep(1)
self._mamma.setstate(CleanedState(self._mamma))
def marinate(self):
print("chicken is in the uncleaned state...first clean it")
pass
def cook(self):
print("chicken is in the uncleaned state...first clean it")
pass
def serve(self):
print("chicken is in the uncleaned state...first clean it")
pass
class CleanedState(State):
def __init__(self, mamma):
self._mamma = mamma
def wash(self):
print("chicken is in the cleaned state...wash already done")
pass
def marinate(self):
print("chicken is in the cleaned state and is marinated. next state will be marinate state")
time.sleep(1)
self._mamma.setstate(MarinateState(self._mamma))
def cook(self):
print("chicken is in the cleaned state...first marinate it")
pass
def serve(self):
print("chicken is in the cleaned state...first marinate it")
pass
class MarinateState(State):
def __init__(self, mamma):
self._mamma = mamma
def wash(self):
print("chicken is in the marinated state...cleaning already done")
pass
def marinate(self):
print("chicken is in the marinated state...marination already done")
pass
def cook(self):
print("chicken is in the marinated state and being cooked. :next state will be cooked state")
time.sleep(1)
self._mamma.setstate(CookedState(self._mamma))
def serve(self):
print("chicken is in the marinated state and being cooked. only after cooking u can serve...")
pass
class CookedState(State):
def __init__(self, mamma):
self._mamma = mamma
def wash(self):
print("chicken has already being cooked")
pass
def marinate(self):
print("chicken has already being cooked")
pass
def cook(self):
print("chicken has already being cooked")
pass
def serve(self):
print("chicken is ready and is served : this is the last state")
time.sleep(1)
print("guest are saying thank you for the meal")
if __name__ == '__main__':
mamma = Mamma(None)
mamma.setstate(UncleanedState(mamma))
mamma.startpreparation()
