I know how to implement method chaining in Python within a single class, but I'm wondering if there is a way to chain methods from different classes, something like:
class C1:
def sayHello(self):
print "hello from c1"
return self
class C2:
def sayHello(self):
print "hello from c2"
return self
c1 = C1()
c2 = C2()
(c1.sayHello()).(c2.sayHello())
Output:
hello from c1
hello from c2
Any ideas?
You can abstract this into a base class (to avoid repeating yourself) and then, as long as they know each other, you can approximate what you originally wanted:
class Base(object):
def sayHello(self, other=None):
print("hello from {self} to {other}".format(self=self, other=other))
return other
def __str__(self):
return type(self).__name__
class C1(Base):
'''C1!'''
class C2(Base):
'''C2!'''
c1 = C1()
c2 = C2()
c1.sayHello(c2).sayHello(c1)
prints:
hello from C1 to C2
hello from C2 to C1
Method chaining is usually only found in APIs where it makes it convenient to perform a sequence of actions on a single object. The question of how to do it with two objects would really depend on how that was meaningful in your API or library. That being said, here's one idea which is completely abstract:
# Untested code
class OtherChain(object):
def __init__(self, other=None):
self._other = other
def sayHello(self):
print "hello from {0}".format(type(self).__name__)
return self._other
class C1(OtherChain):
pass
class C2(OtherChain):
pass
c2 = C2()
c1 = C1(c2)
c1.sayHello().sayHello()
# Output:
# hello from C1
# hello from C2
Of course this code has issues since doing c1.sayHello().sayHello().sayHello() would cause an AttributeError (I think). Those kinds of details would probably get worked out if this code had some kind of context in a library where it was more meaningful.
