existing properties on typeclasses and their database objects. Unless
you know what you are doing, this can cause lots of trouble.
::
rose.msg("hello") # this uses the in-built msg() method rose.msg = "Ouch!" # this OVERLOADS the msg() method with a string rose.msg("hello") # this now a gives traceback!
Overloading ``msg()`` with a string is a very bad idea since Evennia
uses this method all the time to send text to you. There are of course
situations when you *want* to overload default methods with your own
implementations - but then you'll hopefully do so intentionally and with
something that works.
::
rose.db.msg = "Ouch" # this stands no risk of overloading msg() rose.msg("hello") # this works as it should
So using ``db``/``ndb`` will always do what you expect and is usually
the safer bet. It also makes it visually clear at all times when you are
# a single value obj.db.test1 = 23 obj.db.test1 = False # a database object (will be stored as dbref) obj.db.test2 = myobj # a list of objects obj.db.test3 = [obj1, 45, obj2, 67] # a dictionary obj.db.test4 = 'str':34, 'dex':56, 'agi':22, 'int':77 # a mixed dictionary/list obj.db.test5 = 'members': [obj1,obj2,obj3], 'enemies':[obj4,obj5] # a tuple with a list in it obj.db.test6 = (1,3,4,8, ["test", "test2"], 9) # a set will still be stored and returned as a list [1,2,3,4,5]! obj.db.test7 = set([1,2,3,4,5]) # in-situ manipulation obj.db.test8 = [1,2,"test":1] obj.db.test8[0] = 4 obj.db.test8[2]["test"] = 5 # test8 is now [4,2,"test":5]
# this will fool the dbobj-check since myobj (a database object) is "hidden" # inside a custom object. This is unsupported and will lead to unexpected # results! class BadStorage(object): pass bad = BadStorage() bad.dbobj = myobj obj.db.test8 = bad # this will likely lead to a traceback
variable (``mylist2``) will *still* be a !PackedList! This means it will
continue to save itself to the database whenever it is updated! This is
important to keep in mind so you are not confused by the results.
::
obj.db.mylist = [1,2,3,4] mylist = obj.db.mylist mylist[3] = 5 # this will also update database print mylist # this is now [1,2,3,5] print mylist.db.mylist # this is also [1,2,3,5]
To "disconnect" your extracted mutable variable from the database you
simply need to convert the PackedList or PackedDict to a normal Python
list or dictionary. This is done with the builtin ``list()`` and
``dict()`` functions. In the case of "nested" lists and dicts, you only
have to convert the "outermost" list/dict in order to cut the entire
structure's connection to the database.
::
obj.db.mylist = [1,2,3,4] mylist = list(obj.db.mylist) # convert to normal list mylist[3] = 5 print mylist # this is now [1,2,3,5] print obj.db.mylist # this remains [1,2,3,4]
Remember, this is only valid for mutable iterables - lists and dicts and
obj.db.mytup = (1,2,[3,4]) obj.db.mytup[0] = 5 # this fails since tuples are immutable obj.db.mytup[2][1] = 5 # this works but will NOT update database since outermost iterable is a tuple print obj.db.mytup[2][1] # this still returns 4, not 5 mytup1 = obj.db.mytup # mytup1 is already disconnected from database since outermost # iterable is a tuple, so we can edit the internal list as we want # without affecting the database.
