Object has no attribute _meta in python Cement App - python-2.7

Question

I am new to python and cement app,
I am just going through the documentation given in cement app and I am facing the following issue
Traceback (most recent call last):
File "/Users/Amith/python/learning/inter.py", line 80, in <module>
app.handler.register(MyHandler)
File "/Users/Amith/python/learning/connectors/lib/python2.7/site-packages/cement/core/handler.py", line 195, in register
if not hasattr(obj._meta, 'label') or not obj._meta.label:
AttributeError: 'MyHandler' object has no attribute '_meta'
I didnt find much help from documentation and verified few other wesites as well.
Please find my code below
from cement.core.foundation import CementApp
from cement.core.interface import Interface, Attribute
from cement.core import interface
from cement.core.handler import CementBaseHandler
def my_validator(klass, obj):
members = [
'_setup',
'do_something',
'my_var',
]
interface.validate(MyInterface, obj, members)
class MyInterface(Interface):
class IMeta:
label = 'myinterface'
validator = my_validator
# Must be provided by the implementation
Meta = Attribute('Handler Meta-data')
my_var = Attribute('A variable of epic proportions.')
def _setup(app_obj):
""" The setup function """
def do_something():
""" This function does something. """
class MyHandler(CementBaseHandler):
class Meta:
interface = MyInterface
label = 'my_handler'
description = 'This handler implements MyInterface'
config_defaults = dict(
foo='bar'
)
my_var = 'This is my var'
def __init__(self):
self.app = None
def _setup(self, app_obj):
self.app = app_obj
def do_something(self):
print "Doing work!"
class MyApp(CementApp):
class Meta:
label = 'myapp'
define_handlers = [MyInterface]
handlers = [MyHandler]
app = CementApp('myapp')
# define interfaces after app is created
app.setup()
print app.config.keys('myapp')
app.config.set('myapp', 'debug', True)
print app.config.keys('myapp')
app.handler.define(MyInterface)
app.handler.register(MyHandler)
app.run()
Any help will be much appriciated

Answer 1

The problem is that MyHandler does not properly sub-class CementBaseHandler. Any methods need to be sub-classed with super()... for example:
class MyHandler(CementBaseHandler):
class Meta:
interface = MyInterface
label = 'my_handler'
description = 'This handler implements MyInterface'
config_defaults = dict(
foo='bar'
)
my_var = 'This is my var'
def __init__(self, *args, **kw):
super(MyHandler, self).__init__(*args, **kw)
# add your code here (if necessary)
def _setup(self, app_obj):
super(MyHandler, self)._setup(app_obj)
# add your code here if necessary
def do_something(self):
print "Doing work!"
Notice the modifications to MyHandler.__init__() and MyHandler._setup() using super()... this fixed the issue for me.
I apologize for the inconvenience in the documentation, and thank you for pointing it out with a proper/working/reproducable example. I've added an issue to the project in Github to have it fixed in the next release.
https://github.com/datafolklabs/cement/issues/423