mirror of https://github.com/kivy/kivy.git
45 lines
1.5 KiB
ReStructuredText
45 lines
1.5 KiB
ReStructuredText
Properties
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----------
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Kivy introduces a new way of declaring properties within a class.
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Before::
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class MyClass(object):
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def __init__(self):
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super(MyClass, self).__init__()
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self.numeric_var = 1
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After, using Kivy's properties::
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class MyClass(EventDispatcher):
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numeric_var = NumericProperty(1)
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Theses properties implement the `Observer pattern
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<http://en.wikipedia.org/wiki/Observer_pattern>`_. They help you to:
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- Easily manipulate widgets defined in the :doc:`/guide/lang`
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- Automatically observe any changes and dispatch functions/code accordingly
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- Check and validate values
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- Optimize memory management
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To use them, **you have to declare them at class level**. That is, directly in
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the class, not in any method of the class. A property is a class attribute
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that will automatically create instance attributes. Each property by default
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provides an ``on_<propertyname>`` event that is called whenever the property's
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state/value changes.
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Kivy provides the following properties:
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:mod:`~kivy.properties.NumericProperty`,
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:mod:`~kivy.properties.StringProperty`,
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:mod:`~kivy.properties.ListProperty`,
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:mod:`~kivy.properties.ObjectProperty`,
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:mod:`~kivy.properties.BooleanProperty`,
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:mod:`~kivy.properties.BoundedNumericProperty`,
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:mod:`~kivy.properties.OptionProperty`,
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:mod:`~kivy.properties.ReferenceListProperty`,
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:mod:`~kivy.properties.AliasProperty`,
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:mod:`~kivy.properties.DictProperty`,
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For an in-depth explaination, take a look at :doc:`/api-kivy.properties`.
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