Export QTableView data with a delegated column to CSV
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@morteza-ali-ahmadi said in Export QTableView data with a delegated column to CSV:
It means that ui->tableView->model() returns the model with original data not delegated ones.
This is because item delegates are a part of the data view, and have nothing to do with the model, which is what you are going through (correctly) in your export code.
I have had this issue in old discussions I raised in this forum. When told to use delegates for output string formatting, I have pointed out that this does not help if you want to export or otherwise use the string representation, and so I see/saw a particular string format as being useful at the model side for other purposes, not just the view side.
You have a couple of choices:
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My original approach was to produce the desired string format in the model's
data(index, role=Qt::DisplayRole)method, so that is simple & easy to use wherever wanted, and would work for you here. However, I was roundly criticised by some experts, whom I have to respect, saying that is not the intention ofQt::DisplayRole. Others have still supported that approach. -
An alternative might be to define a user role for this, I don't know if experts would be happier with this.
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Otherwise you need to factor out the
QDateTime::toString()portion of your delegate code and move it to some shared area accessible both to your delegate and your model-exporting code, and call it separately from both.
Incidentally, in your delegate code if you don't need all the
drawItemText()call stuff you can simply assign the desired the desired text viaoption.text = strand call the baseQStyledItemDelegate::paint(). -
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@JonB Thanks for your response. I prefer to use your original approach compare to the second and third choices, but how can I produce the desired string format in the models
data(index, role=Qt::DisplayRole)?QVariant MyModel::data(const QModelIndex &index, int role /*= Qt::DisplayRole*/) const { if (!index.isValid()) return QVariant(); QVariant v = BaseModel::data(index, role); if (role == Qt::DisplayRole) if (isTimeStampColumn(index.column())) { double value = v.toDouble(); ... return QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime).toString("yyyy-MM-dd HH:mm:ss.zzz"); } return v; }If you want to correctly sort on this column, you ought have a sort role which returns the base data value, not the string.
Remember from what I said above, don't blame me if one of the expert critics --- @VRonin, IIRC, though I might be mistaken --- calls for your beheading for using this approach... ;-)
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What I would do:
In the delegate, don't reimplementpaint(), butdisplayText()(it's also a lot easier than what you did):class TimeDgDelegate : public QStyledItemDelegate{ Q_OBJECT public: using QStyledItemDelegate::QStyledItemDelegate; QString displayText(const QVariant &value, const QLocale &locale) const override{ double value = value.toDouble(); double qd_ts = value*1.25/(256.0*256.0); qd_ts += 315964800000; return locale.toString(QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime),QStringLiteral("yyyy-MM-dd HH:mm:ss.zzz")); } };Then your csv export would become:
for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { const QModelIndex idx = model->index(i,j); textData += ui->tableView->itemDelegate(idx)->displayText(model->data(idx),locale()) + QLatin1Char(','); } textData += QLatin1Char('\n'); }P.S.
Probably doesn't apply here but generally csv exporting requires you to escape,and"characters in the data"La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
~Napoleon BonaparteOn a crusade to banish setIndexWidget() from the holy land of Qt
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QVariant MyModel::data(const QModelIndex &index, int role /*= Qt::DisplayRole*/) const { if (!index.isValid()) return QVariant(); QVariant v = BaseModel::data(index, role); if (role == Qt::DisplayRole) if (isTimeStampColumn(index.column())) { double value = v.toDouble(); ... return QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime).toString("yyyy-MM-dd HH:mm:ss.zzz"); } return v; }If you want to correctly sort on this column, you ought have a sort role which returns the base data value, not the string.
Remember from what I said above, don't blame me if one of the expert critics --- @VRonin, IIRC, though I might be mistaken --- calls for your beheading for using this approach... ;-)
@JonB Thank you again for your codes.
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What I would do:
In the delegate, don't reimplementpaint(), butdisplayText()(it's also a lot easier than what you did):class TimeDgDelegate : public QStyledItemDelegate{ Q_OBJECT public: using QStyledItemDelegate::QStyledItemDelegate; QString displayText(const QVariant &value, const QLocale &locale) const override{ double value = value.toDouble(); double qd_ts = value*1.25/(256.0*256.0); qd_ts += 315964800000; return locale.toString(QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime),QStringLiteral("yyyy-MM-dd HH:mm:ss.zzz")); } };Then your csv export would become:
for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { const QModelIndex idx = model->index(i,j); textData += ui->tableView->itemDelegate(idx)->displayText(model->data(idx),locale()) + QLatin1Char(','); } textData += QLatin1Char('\n'); }P.S.
Probably doesn't apply here but generally csv exporting requires you to escape,and"characters in the data@VRonin
Thanks for posting. I forget about justQStyledItemDelegate::displayText(), that's a good one to remember.Assuming you are indeed the expert poster in the past about use of
Qt::DisplayRoleI recall, and who called for my execution :) You don't like that use of the model/display role, and now I feel similarly uncomfortable about your use of anythingQStyledItemDelegate,ui->tableView->itemDelegate(idx), when you are exporting model data to CSV. Your export requires access to a UI table view, but the format for CSV export has nothing to do with any model views, and there is no reason to suppose exporting code would have any UI access at all, or even be a GUI application. IMHO. We're probably not going to agree ;-) -
What I would do:
In the delegate, don't reimplementpaint(), butdisplayText()(it's also a lot easier than what you did):class TimeDgDelegate : public QStyledItemDelegate{ Q_OBJECT public: using QStyledItemDelegate::QStyledItemDelegate; QString displayText(const QVariant &value, const QLocale &locale) const override{ double value = value.toDouble(); double qd_ts = value*1.25/(256.0*256.0); qd_ts += 315964800000; return locale.toString(QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime),QStringLiteral("yyyy-MM-dd HH:mm:ss.zzz")); } };Then your csv export would become:
for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { const QModelIndex idx = model->index(i,j); textData += ui->tableView->itemDelegate(idx)->displayText(model->data(idx),locale()) + QLatin1Char(','); } textData += QLatin1Char('\n'); }P.S.
Probably doesn't apply here but generally csv exporting requires you to escape,and"characters in the data@VRonin Thank you very much, yes, it could solve my problem with a better implementation.
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@VRonin
Thanks for posting. I forget about justQStyledItemDelegate::displayText(), that's a good one to remember.Assuming you are indeed the expert poster in the past about use of
Qt::DisplayRoleI recall, and who called for my execution :) You don't like that use of the model/display role, and now I feel similarly uncomfortable about your use of anythingQStyledItemDelegate,ui->tableView->itemDelegate(idx), when you are exporting model data to CSV. Your export requires access to a UI table view, but the format for CSV export has nothing to do with any model views, and there is no reason to suppose exporting code would have any UI access at all, or even be a GUI application. IMHO. We're probably not going to agree ;-)@JonB said in Export QTableView data with a delegated column to CSV:
Your export requires access to a UI table view, but the format for CSV export has nothing to do with any model views, and there is no reason to suppose exporting code would have any UI access at all, or even be a GUI application
I think we actually agree on this one. The clean way here is to have a function that handles the conversion of data from double to QDate. The delegate will call it and then format it as a string to display, the csv serialiser will call it and then save the QDate to csv.
Assuming you are indeed the expert poster in the past about use of Qt::DisplayRole I recall, and who called for my execution
This is a very corner case in which your approach doesn't do much harm and can be used. if, however, the date format was
dd-MM-yyyy HH:mm:ss.zzzthen your solution would break sorting in the table (as it would sort as string, not as dates)"La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
~Napoleon BonaparteOn a crusade to banish setIndexWidget() from the holy land of Qt
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@JonB said in Export QTableView data with a delegated column to CSV:
Your export requires access to a UI table view, but the format for CSV export has nothing to do with any model views, and there is no reason to suppose exporting code would have any UI access at all, or even be a GUI application
I think we actually agree on this one. The clean way here is to have a function that handles the conversion of data from double to QDate. The delegate will call it and then format it as a string to display, the csv serialiser will call it and then save the QDate to csv.
Assuming you are indeed the expert poster in the past about use of Qt::DisplayRole I recall, and who called for my execution
This is a very corner case in which your approach doesn't do much harm and can be used. if, however, the date format was
dd-MM-yyyy HH:mm:ss.zzzthen your solution would break sorting in the table (as it would sort as string, not as dates)@VRonin said in Export QTableView data with a delegated column to CSV:
I think we actually agree on this one.
Amazing :)
This is a very corner case in which your approach doesn't do much harm
It is good to know that at worst I am "harmless" ;-)
The clean way here is to have a function that handles the conversion of data from double to QDate. The delegate will call it and then format it as a string to display, the csv serialiser will call it and then save the QDate to csv.
I suggested that as my 3rd alternative.
then your solution would break sorting in the table (as it would sort as string, not as dates)
Absolutely, and I thought I typed into my answer about if you did this you need to use a different sort role if you sort, but maybe I deleted that. But yes people should bear this in mind.
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What I would do:
In the delegate, don't reimplementpaint(), butdisplayText()(it's also a lot easier than what you did):class TimeDgDelegate : public QStyledItemDelegate{ Q_OBJECT public: using QStyledItemDelegate::QStyledItemDelegate; QString displayText(const QVariant &value, const QLocale &locale) const override{ double value = value.toDouble(); double qd_ts = value*1.25/(256.0*256.0); qd_ts += 315964800000; return locale.toString(QDateTime::fromMSecsSinceEpoch(qd_ts, Qt::LocalTime),QStringLiteral("yyyy-MM-dd HH:mm:ss.zzz")); } };Then your csv export would become:
for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { const QModelIndex idx = model->index(i,j); textData += ui->tableView->itemDelegate(idx)->displayText(model->data(idx),locale()) + QLatin1Char(','); } textData += QLatin1Char('\n'); }P.S.
Probably doesn't apply here but generally csv exporting requires you to escape,and"characters in the data@VRonin Does your solution convert epochs format to string one twice? i.e. for each database record in your solution,
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Conversion with
displayTextfunction is used to display "yyyy-MM-dd HH:mm:ss.zzz" format in QTableView and, -
Conversion with
displayTextfunction is used to store "yyyy-MM-dd HH:mm:ss.zzz" format in CSV.
Is it right?
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correct, you are basically using
displayTextas a fancytoString().Also, just to be clear, the delegate repaints on demand and doesn't cache the
displayTextso it's actually calculated every time a repaints happens@VRonin, So I think the combination of your solution and the third solution of @JonB is the best choice. It means that, I can override
displayText()instead ofpaint()and use a functionXwithin that which handles the conversion of data from double to "dd-MM-yyyy HH:mm:ss.zzz". Also, theXfunction can be used in export to CSV procedure. -
@VRonin, So I think the combination of your solution and the third solution of @JonB is the best choice. It means that, I can override
displayText()instead ofpaint()and use a functionXwithin that which handles the conversion of data from double to "dd-MM-yyyy HH:mm:ss.zzz". Also, theXfunction can be used in export to CSV procedure.@morteza-ali-ahmadi Yes.
