@pyqtslot返回值未定义

Question

我有一个使用设置的QML应用程序。因此，我创建了一个python插槽，用于读取settings.toml，并返回值。我已经正确设置了上下文属性，并且可以调用其他函数，而无需从QML返回值，不会出现问题

...
class Settings(QObject)
    @pyqtSlot(str, str)
    def getSettings(self, category, key):
        try:
            with open("settings.toml", "r") as settings:
                toml_object = toml.load(settings)
            return str(toml_object[category][key])
        except FileNotFoundError:
            self.settingsFileNotFound.emit()
        except toml.TomlDecodeError:
            self.settingsError.emit()
        except BaseException:
            self.fatalError.emit()
...

{}原子看起来像这样

...
[last-used-font-settings]
font = "Arial"
... 

从python打印函数时，它会按预期工作

...
print(Settings.getSettings("last-used-font-settings", "font")) # Returns Arial
...

但从qml登录时：

...   
Component.onCompleted: console.log(Settings.getSettings("last-used-font-settings", "font"))
/* Returns qml: undefined */
...

如何解决这个问题？ 我不太擅长创建@pyqtProperty，但如果我成功创建了一个，我肯定不想为每个值创建一个属性

你看，信号不能用于这个目的（

Answer 1

如果要从python返回值，则必须在pyqtSlot中使用“result”：

import os

from PyQt5.QtCore import pyqtProperty, pyqtSlot, QObject, QUrl
from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQml import QQmlApplicationEngine

import toml

CURRENT_DIR = os.path.dirname(os.path.realpath(__file__))


class Settings(QObject):
    def __init__(self, parent=None):
        super().__init__(parent)
        self._error_string = ""

    @pyqtProperty(str, constant=True)
    def errorString(self):
        return self._error_string

    @pyqtSlot(result=bool)
    def hasError(self):
        return bool(self.errorString)

    @pyqtSlot(str, str, result=str)
    def getSettings(self, category, key):
        self._error_string = ""
        error_string = ""
        value = ""
        try:
            with open(os.path.join(CURRENT_DIR, "settings.toml"), "r") as settings:
                toml_object = toml.load(settings)
                value = str(toml_object[category][key])
        except FileNotFoundError:
            error_string = "FileNotFoundError"
        except toml.TomlDecodeError:
            error_string = "TomlDecodeError"
        except Exception as e:
            error_string = str(e)
        self._error_string = error_string
        return value


if __name__ == "__main__":
    import sys

    app = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()
    settings = Settings()
    engine.rootContext().setContextProperty("Settings", settings)

    filename = os.path.join(CURRENT_DIR, "main.qml")
    engine.load(QUrl.fromLocalFile(filename))

    if not engine.rootObjects():
        sys.exit(-1)
    sys.exit(app.exec())

import QtQuick 2.12
import QtQuick.Controls 2.12

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    Component.onCompleted: {
        var value = Settings.getSettings("last-used-font-settings", "font")
        if(Settings.hasError()){
            console.error(Settings.errorString)
        }
        else{
            console.log(value)
        }
    }
}