Range-based for loop for a QList
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Hello all,
Please take a look at my project.
ListAdd.h:#ifndef LISTADD_H #define LISTADD_H #include <QDialog> #include <QAbstractButton> class QPushButton; class QListWidget; class QComboBox; class QDialogButtonBox; class ListAdd : public QDialog { Q_OBJECT public: ListAdd(QWidget *parent = nullptr); private slots: void addData(); void save(); private: void load(); void btnClicked(QAbstractButton*); QComboBox* combo = nullptr; QPushButton* add = nullptr; QListWidget* list = nullptr; QDialogButtonBox* dBtBox = nullptr; }; #endif // LISTADD_HListAdd.cpp:#include "listadd.h" #include <QListWidget> #include <QComboBox> #include <QPushButton> #include <QDialogButtonBox> #include <QHBoxLayout> #include <QVBoxLayout> #include <QSettings> #include <QMessageBox> #include <QVariant> ListAdd::ListAdd(QWidget *parent) : QDialog(parent) { combo = new QComboBox; combo->setEditable(true); add = new QPushButton(tr("&Add")); list = new QListWidget; list->setSelectionMode(QAbstractItemView::ExtendedSelection); dBtBox = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel); dBtBox->setEnabled(true); dBtBox->addButton("Clear", QDialogButtonBox::ButtonRole::ActionRole); dBtBox->addButton("Remove", QDialogButtonBox::ButtonRole::ActionRole); QHBoxLayout* topLayout = new QHBoxLayout; topLayout->addWidget(combo); topLayout->addWidget(add); QVBoxLayout* mainLayout = new QVBoxLayout; mainLayout->addLayout(topLayout); mainLayout->addWidget(list); mainLayout->addWidget(dBtBox); setLayout(mainLayout); connect(add, &QPushButton::clicked, this, &ListAdd::addData); connect(dBtBox, &QDialogButtonBox::clicked, this, &ListAdd::btnClicked); load(); } //******************************************* void ListAdd::addData() { if(combo->findText(combo->currentText()) < 0) combo->addItem(combo->currentText()); list->addItem(combo->currentText()); } //************************************************************* void ListAdd::save() { QSettings settings("Me", "CS Company"); settings.clear(); settings.setValue("text",combo->currentText()); settings.beginWriteArray("combo"); for (int i=0; i<combo->count();i++) { settings.setArrayIndex(i); settings.setValue("item", combo->itemText(i)); } settings.endArray(); settings.beginWriteArray("list"); for (int i=0; i<list->count();i++) { settings.setArrayIndex(i); settings.setValue("item", list->item(i)->text()); } settings.endArray(); } //******************************************************** void ListAdd::load() { QSettings settings("Me", "CS Company"); combo->setCurrentText(settings.value("text", "").toString()); int comboSize = settings.beginReadArray("combo"); for (int i=0; i<comboSize;i++) { settings.setArrayIndex(i); combo->addItem(settings.value("item", "").toString()); } settings.endArray(); int listSize = settings.beginReadArray("list"); for (int i=0; i<listSize;i++) { settings.setArrayIndex(i); list->addItem(settings.value("item", "").toString()); } settings.endArray(); } //******************************************************************** void ListAdd::btnClicked(QAbstractButton* button) { if(button->text().contains("OK")) { save(); QMessageBox::information(this, "Saved", "Your data is saved! Please re-open the application"); } else if(button->text().contains("Cancel")) { QMessageBox::information(this, "Quit", "Your data is being lost"); accept(); } else if(button->text().contains("Clear")) { list->clear(); combo->clear(); } else if(button->text().contains("Remove")) { QList<QListWidgetItem*> items = list->selectedItems(); for(auto& item : items) { list->removeItemWidget(item); delete item; } } }The question is about the
else-ifcondition above, which is, why withoutdelete item;, won't the item be removed from the list, please?@tomy said in Range-based for loop for a QList:
for(auto& item : items) { list->removeItemWidget(item); delete item; }Not sure it's safe to delete an item while looping over the list
Safer to do:for(auto& item : items) { list->removeItemWidget(item); } qDeletAll(items); -
I hope I get answers for the last two questions I asked, "entirely" and "destructor". Should I make separate threads for them?
@Bonnie
Well, there's no widget set by setItemWidget; I used selectionItems. So you mean that function neither removes any item in the list nor is it needed in the code?It may make sense not to delete the cells of the list while you're still connected to it, but except for that is there any rationale?
So if I use this for that last condition, it's the easiest and best method!else if(button->text().contains("Remove")) { qDeleteAll(list->selectedItems()); -
I hope I get answers for the last two questions I asked, "entirely" and "destructor". Should I make separate threads for them?
@Bonnie
Well, there's no widget set by setItemWidget; I used selectionItems. So you mean that function neither removes any item in the list nor is it needed in the code?It may make sense not to delete the cells of the list while you're still connected to it, but except for that is there any rationale?
So if I use this for that last condition, it's the easiest and best method!else if(button->text().contains("Remove")) { qDeleteAll(list->selectedItems()); -
@tomy Yes, if you open qlistwidget.h, you can see that:
inline void QListWidget::removeItemWidget(QListWidgetItem *aItem) { setItemWidget(aItem, nullptr); }I took a look twice on the task that removeItemWidget does, but couldn't understand this, since the setItemWidget looks complicated.
Will you explain what that remove function does in my code, please. This way it becomes clearer I suppose. -
@tomy said in Range-based for loop for a QList:
for(auto& item : items) { list->removeItemWidget(item); delete item; }Not sure it's safe to delete an item while looping over the list
Safer to do:for(auto& item : items) { list->removeItemWidget(item); } qDeletAll(items);@Asperamanca said in Range-based for loop for a QList:
Safer to do:
In this case it's not needed - it just adds another loop for nothing.
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I took a look twice on the task that removeItemWidget does, but couldn't understand this, since the setItemWidget looks complicated.
Will you explain what that remove function does in my code, please. This way it becomes clearer I suppose.@tomy said in Range-based for loop for a QList:
Will you explain what that remove function does in my code, please.
It removes the widget from the view, nothing more (and exactly what the function name states...)
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@tomy said in Range-based for loop for a QList:
Will you explain what that remove function does in my code, please.
It removes the widget from the view, nothing more (and exactly what the function name states...)
By "from the view" you mean "disappearing" right? But it does nothing to be seen.
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I took a look twice on the task that removeItemWidget does, but couldn't understand this, since the setItemWidget looks complicated.
Will you explain what that remove function does in my code, please. This way it becomes clearer I suppose.@tomy As I said, if you haven't called setItemWidget to set a widget, then it does nothing at all.
[ADDED]
And setItemWidget is not that complicated.
You can use it to set a widget to a item, maybe a button, a combox, or any kind of widget.
When the item is visible in the list view, the widget will be shown on the item rect.
So by removeItemWidget, you can remove that widget. -
@tomy said in Range-based for loop for a QList:
Will you explain what that remove function does in my code, please.
It removes the widget from the view, nothing more (and exactly what the function name states...)
This post is deleted! -
@Asperamanca said in Range-based for loop for a QList:
Safer to do:
In this case it's not needed - it just adds another loop for nothing.
This post is deleted! -
@tomy As I said, if you haven't called setItemWidget to set a widget, then it does nothing at all.
[ADDED]
And setItemWidget is not that complicated.
You can use it to set a widget to a item, maybe a button, a combox, or any kind of widget.
When the item is visible in the list view, the widget will be shown on the item rect.
So by removeItemWidget, you can remove that widget.
