@pyqtslot 返回值未定义

Question

我有一个使用设置的 QML 应用程序。所以我创建了一个 python 槽来读取settings.toml, 并返回值。我已经正确设置了上下文属性，并且可以毫无问题地调用其他函数，而无需从 QML 获取返回值。

...

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()

...

tomlsettings.看起来像这样。

...

[last-used-font-settings]

font = "Arial"

... 

从 python 打印函数时，它按预期工作。

...

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

...

但是当从 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，但如果我设法创建一个，我绝对不想为每个值创建一个属性！

你看，信号不能用于此目的。:(

Answer 1

如果你想从 python 返回一个值，那么你必须在 pyqtSlot 中使用“result”：import osfrom PyQt5.QtCore import pyqtProperty, pyqtSlot, QObject, QUrlfrom PyQt5.QtGui import QGuiApplicationfrom PyQt5.QtQml import QQmlApplicationEngineimport tomlCURRENT_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 valueif __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 2.12import QtQuick.Controls 2.12ApplicationWindow {    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)        }    }}