Michael George Lerner a écrit :
Hi,
As part of my GUI, I have lots of fields that people can fill in,
defined like this:
self.selection = Pmw.EntryField(group.interior(),
labelpos='w',
label_text='Selection to use:
',
value='(polymer)',
)
I then use self.selection.get_value() and self.selection.set_value(),
and those two functions are the only ways in which I care about
self.selection. I've never really used properties, getters or setters
before. I tried this, but it didn't work:
def __init__(self):
self._selection = Pmw.EntryField(group.interior(),
labelpos='w',
label_text='Selection to use:
',
value='(polymer)',
)
self.selection = property(self._selection.get_value
(),self._selection.set_value())
What you're passing here are the results of the calls to .get_value and
.set_value, not the methods themselves. You'd want:
self.selection = property(
self._selection.get_value,
self._selection.set_value
)
But as Steven already mentioned, property only works as a class
attribute, not as an instance attribute. What you need here is:
class Parrot(object):
def __init__(self):
self._selection = Pmw.EntryField(...)
selection = property(
lambda self: self._selection.get_value(),
lambda self, value: self._selection.set_value(value)
)
Of course, I really have ~40 things that I'd like to do this for, not
just one, so I'd like to find a fairly concise syntax.
the property object is just one possible application of the descriptor
protocol. You could write your own custom descriptor (warning: untested
code, may contains typos etc):
class FieldProperty(object):
def __init__(self, fieldname):
self._fieldname = fieldname
def __get__(self, instance, cls):
if instance is None:
# can't work on the class itself
return self
return getattr(instance, self._fieldname).get_value()
def __set__(self, instance, value):
getattr(instance, self._fieldname).set_value(value)
class Parrot(object):
def __init__(self):
self._selection = Pmw.EntryField(...)
selection = FieldProperty("_selection")
HTH
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