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Kivy Data Model Bridge -- A set of classes to allow the effortless bridging of of a data model written in standard python and a UI which is meant to automatically update to display the results of the data model
"""
Allow the simple creation of kivy UIs for arbitrary python object. The UI
will automatically update as the underlying python model changes, provided any
function on the UI side that changes the underlying data model use the
"update" decorator.
"""
import kivy
kivy.require('1.7.0')
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.properties import StringProperty
from kivy.event import EventDispatcher
from kivy.lang import Builder
##################
# DATA MODEL SIDE
##################
class DataModel(object):
def __init__(self):
self.a = 'This is a'
self.b = 'This is b'
@property
def c(self):
return self.a + '\nand\n' + self.b
# Create an instance of the data model that will be used in both the
# data processing and UI display sides of things
common_data_model = DataModel()
##################
# BRIDGE
##################
class UI_DataModelMeta(type):
def __new__(meta, name, bases, dct):
# Create kivy StringProperty objects for all the attributes
# in the underlying data model
added_attributes = []
for attr in dir(common_data_model):
if not attr.startswith('_'):
##print "Making attribute %s" % attr
assert attr not in dir(EventDispatcher())
dct[attr] = StringProperty('INIT')
added_attributes.append(attr)
# Let the UI_DataModel know what attributes are from the common model
dct['_model_attr'] = added_attributes
return super(UI_DataModelMeta, meta).__new__(meta, name, bases, dct)
class UI_DataModel(EventDispatcher):
__metaclass__ = UI_DataModelMeta
def __getattribute__(self, key):
##print ">> Trying to get %s" % key
if key == '_model_attr':
return object.__getattribute__(self, key)
elif key in self._model_attr:
##print " INTERCEPTED!"
# Get the value of this key from the common data model
val = str(getattr(common_data_model, key))
##print " val is %s" % val
# Invoke kivy's StringProperty setter by setting our attribute
setattr(self, key, val)
# Proceed as normal
return EventDispatcher.__getattribute__(self, key)
else:
##print " Pushing up to base class"
return EventDispatcher.__getattribute__(self, key)
def update(self, func):
"""Decorator to put around any UI function that update the common
data model"""
def wrapper(*args, **kwargs):
# Execute function as normal
ret = func(*args, **kwargs)
# Update UI Data Model wrapper
for attr in self._model_attr:
getattr(self, attr)
return ret
return wrapper
##################
# UI SIDE
##################
Builder.load_string("""
<RootWidget>:
cols: 2
Label:
text: "Attribute a:"
Label:
text: root.ui_data_model.a
Label:
text: "Attribute b:"
Label:
text: root.ui_data_model.b
Label:
text: "Attribute c:"
Label:
text: root.ui_data_model.c
Button:
text: "Make data_model.a longer"
on_press: root.button_press()
Button:
text: "Make data_model.b shorter"
on_press: root.button_press2()
""")
class RootWidget(GridLayout):
ui_data_model = UI_DataModel()
@ui_data_model.update
def button_press(self, *args):
# Make sure you modify the common data model, not the UI's
# data model wrapper
common_data_model.a = 'This is a and it is really long now'
##print common_data_model.c
##print self.ui_data_model.c
##print self.ui_data_model.a
@ui_data_model.update
def button_press2(self, *args):
common_data_model.b = 'B'
##print common_data_model.c
##print self.ui_data_model.c
class TestApp(App):
def build(self):
return RootWidget()
app = TestApp()
app.run()
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