= State Programming =

=== Why, When ===

Very often, the response of a function will depend on the state of this object. With this pattern, It's easy to do such a thing ! You just have to write several sub-classes, each per state, inherit the State class and call the setState when the object need to change state.

=== Code ===
{{{
#!python
# Code is Public Domain.
class State:
    
    def setState(self,stateClass):
        #print stateClass.__dict__
        for (name,attr) in stateClass.__dict__.iteritems():
            if not name.startswith('_') and callable(attr):
                f = getattr(stateClass,name)
                l = f.__get__(self,self.__class__)
                setattr(self,name,l)
}}}

=== Example ===
{{{
#!python
# Code is Public Domain.
class test(State):
    def __init__(self,a):
        self.a = a
    
    def showMe(self):
        print self.a

    def showYou(self,other):
        print self.a,other

    def changeToOne(self):
        self.setState(StateOne)

    def changeToTwo(self):
        self.setState(StateTwo)

class StateOne(test):

    def showMe(self):
        print self.a,'State One'

    def showYou(self,other):
        print self.a,'State One',other

class StateTwo(test):

    def showMe(self):
        print self.a,'State Two'

    def showYou(self,other):
        print self.a,'State Two',other
        

t1 = test('t1')
t2 = test('t2')
t1.showMe()
t2.showMe()
t1.showYou("you")
t1.changeToOne()
t1.showMe()
t2.changeToTwo()
t2.showMe()
t1.showYou("you")
t1.changeToTwo()
t2.changeToOne()
t1.showMe()
t2.showMe()
t1.showYou("you")
t2.showYou('you')
}}}

Output is
{{{  
t1
t2
t1 you
t1 State One
t2 State Two
t1 State One you
t1 State Two
t2 State One
t1 State Two you
t2 State One you
}}}