diff options
Diffstat (limited to 'libbe')
| -rw-r--r-- | libbe/storage/util/properties.py | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/libbe/storage/util/properties.py b/libbe/storage/util/properties.py index f48cfa0..55bac85 100644 --- a/libbe/storage/util/properties.py +++ b/libbe/storage/util/properties.py @@ -303,12 +303,14 @@ def cached_property(generator, initVal=None, mutable=False): return funcs return decorator -def primed_property(primer, initVal=None): +def primed_property(primer, initVal=None, unprimeableVal=None): """ Just like a cached_property, except that instead of returning a - new value and running fset to cache it, the primer performs some + new value and running fset to cache it, the primer attempts some background manipulation (e.g. loads data into instance.settings) - such that a _second_ pass through fget succeeds. + such that a _second_ pass through fget succeeds. If the second + pass doesn't succeed (e.g. no readable storage), we give up and + return unprimeableVal. The 'cache' flag becomes a 'prime' flag, with priming taking place whenever ._<name>_prime is True, or is False or missing and @@ -326,6 +328,8 @@ def primed_property(primer, initVal=None): if prime == True or (prime == False and value == initVal): primer(self) value = fget(self) + if prime == False and value == initVal: + return unprimeableVal return value funcs["fget"] = _fget return funcs @@ -543,13 +547,14 @@ if libbe.TESTING == True: def testPrimedLocalProperty(self): class Test(object): def prime(self): - self.settings["PRIMED"] = "initialized" + self.settings["PRIMED"] = self.primeVal @Property - @primed_property(primer=prime, initVal=None) + @primed_property(primer=prime, initVal=None, unprimeableVal=2) @settings_property(name="PRIMED") def x(): return {} def __init__(self): self.settings={} + self.primeVal = "initialized" t = Test() self.failIf("_PRIMED_prime" in dir(t), getattr(t, "_PRIMED_prime", None)) @@ -564,6 +569,10 @@ if libbe.TESTING == True: t._PRIMED_prime = False t.x = 3 self.failUnless(t.x == 3, t.x) + # test unprimableVal + t.x = None + t.primeVal = None + self.failUnless(t.x == 2, t.x) def testChangeHookLocalProperty(self): class Test(object): def _hook(self, old, new): |