Jer*_*imo 6 python properties pyqt
我目前正在寻找一种使用 PyQt5 的QWebEngineView使用 Python 和 HTML/CSS/JS 创建 GUI 桌面应用程序的方法。
在我的小演示应用程序中，我使用QWebChannel发布 Python QObject到 JavaScript 端，以便数据可以共享和来回传递。到目前为止，共享和连接插槽和信号工作正常。
我在同步简单（属性）值时遇到了困难。从我读过的内容来看，要走的路是通过装饰的 getter 和 setter 函数在共享 QObject 中实现一个 pyqtProperty，并在 setter 中发出一个额外的信号，用于在值发生变化时通知 JavaScript。下面的代码显示了这一点，到目前为止它工作正常：
import sys
from PyQt5.QtCore import QObject, pyqtSlot, pyqtProperty, pyqtSignal
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWebChannel import QWebChannel
from PyQt5.QtWebEngineWidgets import QWebEngineView, QWebEnginePage
class HelloWorldHtmlApp(QWebEngineView):
html = '''
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<script src="qrc:///qtwebchannel/qwebchannel.js"></script>
<script>
var backend;
new QWebChannel(qt.webChannelTransport, function (channel) {
backend = channel.objects.backend;
});
</script>
</head>
<body> <h2>HTML loaded.</h2> </body>
</html>
'''
def __init__(self):
super().__init__()
# setup a page with my html
my_page = QWebEnginePage(self)
my_page.setHtml(self.html)
self.setPage(my_page)
# setup channel
self.channel = QWebChannel()
self.backend = self.Backend(self)
self.channel.registerObject('backend', self.backend)
self.page().setWebChannel(self.channel)
class Backend(QObject):
""" Container for stuff visible to the JavaScript side. """
foo_changed = pyqtSignal(str)
def __init__(self, htmlapp):
super().__init__()
self.htmlapp = htmlapp
self._foo = "Hello World"
@pyqtSlot()
def debug(self):
self.foo = "I modified foo!"
@pyqtProperty(str, notify=foo_changed)
def foo(self):
return self._foo
@foo.setter
def foo(self, new_foo):
self._foo = new_foo
self.foo_changed.emit(new_foo)
if __name__ == "__main__":
app = QApplication.instance() or QApplication(sys.argv)
view = HelloWorldHtmlApp()
view.show()
app.exec_()
在连接调试器的情况下开始这个，我可以backend.debug()在 JavaScript 控制台中调用插槽，这会导致值backend.foo“我修改了 foo！” 之后，这意味着 Python 代码成功地更改了 JavaScript 变量。
不过这有点乏味。对于我想分享的每一个价值，我都必须
self._foo）QObject身体内产生信号有没有更简单的方法来实现这一目标？理想情况下某种单行声明？也许使用类或函数来打包所有内容？我将如何将其绑定到QObject稍后？我在想像
# in __init__
self.foo = SyncedProperty(str)
这可能吗？谢谢你的想法！
一种方法是使用元类：
class Property(pyqtProperty):
def __init__(self, value, name='', type_=None, notify=None):
if type_ and notify:
super().__init__(type_, self.getter, self.setter, notify=notify)
self.value = value
self.name = name
def getter(self, inst=None):
return self.value
def setter(self, inst=None, value=None):
self.value = value
getattr(inst, '_%s_prop_signal_' % self.name).emit(value)
class PropertyMeta(type(QObject)):
def __new__(mcs, name, bases, attrs):
for key in list(attrs.keys()):
attr = attrs[key]
if not isinstance(attr, Property):
continue
value = attr.value
notifier = pyqtSignal(type(value))
attrs[key] = Property(
value, key, type(value), notify=notifier)
attrs['_%s_prop_signal_' % key] = notifier
return super().__new__(mcs, name, bases, attrs)
class HelloWorldHtmlApp(QWebEngineView):
...
class Backend(QObject, metaclass=PropertyMeta):
foo = Property('Hello World')
@pyqtSlot()
def debug(self):
self.foo = 'I modified foo!'
感谢您的元类想法，我稍微修改了它，以便与包含多个实例的类正常工作。我面临的问题是该值存储在其Property自身中，而不是存储在类实例属性中。为了清楚起见，我还将Property全班分成了两个班级。
class PropertyMeta(type(QtCore.QObject)):
def __new__(cls, name, bases, attrs):
for key in list(attrs.keys()):
attr = attrs[key]
if not isinstance(attr, Property):
continue
initial_value = attr.initial_value
type_ = type(initial_value)
notifier = QtCore.pyqtSignal(type_)
attrs[key] = PropertyImpl(
initial_value, name=key, type_=type_, notify=notifier)
attrs[signal_attribute_name(key)] = notifier
return super().__new__(cls, name, bases, attrs)
class Property:
""" Property definition.
This property will be patched by the PropertyMeta metaclass into a PropertyImpl type.
"""
def __init__(self, initial_value, name=''):
self.initial_value = initial_value
self.name = name
class PropertyImpl(QtCore.pyqtProperty):
""" Actual property implementation using a signal to notify any change. """
def __init__(self, initial_value, name='', type_=None, notify=None):
super().__init__(type_, self.getter, self.setter, notify=notify)
self.initial_value = initial_value
self.name = name
def getter(self, inst):
return getattr(inst, value_attribute_name(self.name), self.initial_value)
def setter(self, inst, value):
setattr(inst, value_attribute_name(self.name), value)
notifier_signal = getattr(inst, signal_attribute_name(self.name))
notifier_signal.emit(value)
def signal_attribute_name(property_name):
""" Return a magic key for the attribute storing the signal name. """
return f'_{property_name}_prop_signal_'
def value_attribute_name(property_name):
""" Return a magic key for the attribute storing the property value. """
return f'_{property_name}_prop_value_'
演示用法：
class Demo(QtCore.QObject, metaclass=PropertyMeta):
my_prop = Property(3.14)
demo1 = Demo()
demo2 = Demo()
demo1.my_prop = 2.7
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