python - QSQLTableModel 中的格式化值出现问题

Question

子类化 QSQLTableModel 并重写数据方法:

class SclDataModel(QSqlTableModel):
    def __init__(self, parent=None):
        super(SclDataModel, self).__init__(parent)

    def data(self, index, role=None):
        if role == Qt.DisplayRole:
            if index.column() == 2 or index.column() == 3:
                val = QSqlTableModel.data(self, index, Qt.DisplayRole) #<--Is set to None on cell edit.
                print('Value={}'.format(val))   
                return '${:,.2f}'.format(val)
            else:
                return super(SclDataModel,self).data(index,role)
        elif role == Qt.TextAlignmentRole:
            return Qt.AlignVCenter | Qt.AlignRight
        else:
            return QVariant()

加载表时，值会正确呈现；但是，当我编辑其中一个项目时，我收到一个错误，该值格式化为 NoneType。奇怪的是，当我插入新行并编辑值时，它的格式正确。

如果我编辑此值，则会收到以下错误:

Value=None
Traceback (most recent call last):
  File "/mnt/DevServer/Python/PPSBooks/SvcData/scldata_browse.py", line 39, in data
    return '${:,.2f}'.format(val)
TypeError: unsupported format string passed to NoneType.__format__

Answer 1

一般来说，不建议修改模型，因为它代表数据，并且在您的情况下，符号 $ 仅是可视的，因此可视化任务是委托(delegate)的:

class MoneyDelegate(QStyledItemDelegate):
    def initStyleOption(self, option, index):
        super(MoneyDelegate, self).initStyleOption(option, index)
        option.text = '${:,.2f}'.format(index.data())
        option.displayAlignment = Qt.AlignVCenter | Qt.AlignRight

...

view = QTableView()
delegate = MoneyDelegate(view)
for i in (2, 3):
    view.setItemDelegateForColumn(i, delegate)

另一方面，如果您要修改数据，默认角色是Qt::DisplayRole:

class SclDataModel(QSqlTableModel):
    def data(self, index, role=Qt.DisplayRole):
        ...

更新:如果要修改编辑器，则必须覆盖委托(delegate)的 createEditor() 方法:

class MoneyDelegate(QStyledItemDelegate):
    def initStyleOption(self, option, index):
        super(MoneyDelegate, self).initStyleOption(option, index)
        option.text = '${:,.2f}'.format(index.data())
        option.displayAlignment = Qt.AlignVCenter | Qt.AlignRight

    def createEditor(self, parent, option, index):
        editor = super(MoneyDelegate, self).createEditor(parent, option, index)
        if any(isinstance(editor, t) for t in (QDoubleSpinBox, QSpinBox)):
            editor.setMinimum(0)
            editor.setMaximum(2**15)
        return editor