python - 类型错误 : A constant property cannot have a WRITE method or a NOTIFY signal

Question

将一些工作 PyQt5 代码移植到 PySide2，我有以下内容:

import sys
from PySide2.QtCore import Property, QObject
from PySide2.QtGui import QGuiApplication


class DataPoint(QObject):
    def __init__(self, timestamp=0, high=0, low=0, parent=None):
        super().__init__(parent)
        self._timestamp = timestamp
        self._high = high
        self._low = low

    @Property(float, constant=True)
    def timestamp(self):
        return self._timestamp

    ...

这是一个暴露给 QML 引擎的只读数据类。

运行时失败:

Traceback (most recent call last):
  line 14, in <module>
    class DataPoint(QObject):
  line 22, in DataPoint
    def timestamp(self):
TypeError: A constant property cannot have a WRITE method or a NOTIFY signal.

Answer 1

这似乎是 PySide2 中的一个错误，它似乎假设如果将 Property 用作 getter 装饰器，则将设置 setter。一个可能的解决方案是不将其用作装饰器，而是在类的范围内使用:

class DataPoint(QObject):
    def __init__(self, timestamp=0.0, high=0, low=0, parent=None):
        super().__init__(parent)
        self._timestamp = timestamp
        self._high = high
        self._low = low

    def timestamp(self):
        return self._timestamp

    <b>timestamp = Property(float, fget=timestamp, constant=True)</b>