How to design the constructor of Manager more cleaner? Is there any pattern for this problem?
class Manager():
def __init__(self, a_1, a_2, a_3, b_1, b_2, b_3):
self.a = A(a_1, a_2, a_3)
self.b = B(b_1, b_2, b_3)
class A():
def __init__(self, a_1, a_2, a_3):
pass
class B():
def __init__(self, b_1, b_2, b_3):
pass
I can think of two appropriate alternatives:
dependency injection Pass instances of objects as constructor parameters. Your modified constructor will look something like this:
...
def __init(self, A, B):
self.a = A
self.b = B
...
builder pattern and probably fluent interface. It's a bit more complex, but covers scaling to several types of buildable objects.
Here's an example:
# source: https://gist.github.com/pazdera/1121157
class Director:
""" Controls the construction process.
Director has a builder associated with him. Director then
delegates building of the smaller parts to the builder and
assembles them together.
"""
__builder = None
def setBuilder(self, builder):
self.__builder = builder
# The algorithm for assembling a car
def getCar(self):
car = Car()
# First goes the body
body = self.__builder.getBody()
car.setBody(body)
# Then engine
engine = self.__builder.getEngine()
car.setEngine(engine)
# And four wheels
i = 0
while i < 4:
wheel = self.__builder.getWheel()
car.attachWheel(wheel)
i += 1
return car
# The whole product
class Car:
""" The final product.
A car is assembled by the `Director' class from
parts made by `Builder'. Both these classes have
influence on the resulting object.
"""
def __init__(self):
self.__wheels = list()
self.__engine = None
self.__body = None
def setBody(self, body):
self.__body = body
def attachWheel(self, wheel):
self.__wheels.append(wheel)
def setEngine(self, engine):
self.__engine = engine
def specification(self):
print "body: %s" % self.__body.shape
print "engine horsepower: %d" % self.__engine.horsepower
print "tire size: %d\'" % self.__wheels[0].size
class Builder:
""" Creates various parts of a vehicle.
This class is responsible for constructing all
the parts for a vehicle.
"""
def getWheel(self): pass
def getEngine(self): pass
def getBody(self): pass
class JeepBuilder(Builder):
""" Concrete Builder implementation.
This class builds parts for Jeep's SUVs.
"""
def getWheel(self):
wheel = Wheel()
wheel.size = 22
return wheel
def getEngine(self):
engine = Engine()
engine.horsepower = 400
return engine
def getBody(self):
body = Body()
body.shape = "SUV"
return body
class NissanBuilder(Builder):
""" Concrete Builder implementation.
This class builds parts for Nissan's family cars.
"""
def getWheel(self):
wheel = Wheel()
wheel.size = 16
return wheel
def getEngine(self):
engine = Engine()
engine.horsepower = 85
return engine
def getBody(self):
body = Body()
body.shape = "hatchback"
return body
# Car parts
class Wheel:
size = None
class Engine:
horsepower = None
class Body:
shape = None
def main():
jeepBuilder = JeepBuilder()
nissanBuilder = NissanBuilder()
director = Director()
# Build Jeep
print "Jeep"
director.setBuilder(jeepBuilder)
jeep = director.getCar()
jeep.specification()
print ""
# Build Nissan
print "Nissan"
director.setBuilder(nissanBuilder)
nissan = director.getCar()
nissan.specification()
if __name__ == "__main__":
main()
