[Development] About ALIAS in Q_PROPERTY
Konstantin Ritt
ritt.ks at gmail.com
Tue Mar 11 11:05:42 CET 2014
2014-03-11 11:57 GMT+02:00 Svetkin Mikhail <mikhail.svetkin at gmail.com>:
> Try initializing that `ui` with 0 and see what happens.
>
> For this, in moc(for ALIAS) can add a check
>
You can not.
>
> Q_PROPERTY(QString label ALIAS AnyCrap
>> m_parent->labelWidget->objectName())
>
>
> This example not valid.
>
> Q_PROPERTY(QString label ALIAS AnyCrap
> m_parent->labelWidget->propertyName).
>
> Where `propertyName` link on Q_PROPERTY(type propertyName)
>
> If the syntax is very complex, it is possible to do so
> Q_PROPERTY(QString label ALIAS AnyCrap m_parent->labelWidget propertyName).
>
> 2014-03-11 15:12 GMT+06:00 Konstantin Ritt <ritt.ks at gmail.com>:
>
> Try initializing that `ui` with 0 and see what happens.
>>
>> Similar for using the property from a destructor or destruction sequence,
>> since moc is unable to track the pointers in use.
>> Also think about objects you don't control, i.e. Q_PROPERTY(QString label
>> ALIAS AnyCrap m_parent->labelWidget->objectName()) ...and so on.
>>
>> Regards,
>> Konstantin
>>
>>
>> 2014-03-11 10:59 GMT+02:00 Svetkin Mikhail <mikhail.svetkin at gmail.com>:
>>
>> Why do you think moc will crash?
>>>
>>>
>>> 2014-03-11 14:30 GMT+06:00 Konstantin Ritt <ritt.ks at gmail.com>:
>>>
>>>> > Would suggest to solve this problem in this way(The code marked as
>>>> duplicate does not need anymore.):
>>>> > Q_PROPERTY(QString <http://qt-project.org/doc/QString.html> label
>>>> ALIAS CustomWidgetFirst ui->custom_widget_first_obj->value ) // where
>>>> "value" property name
>>>>
>>>> I don't think moc is able to guarantee no crash at
>>>> `ui->custom_widget_first_obj->value`. So you're trading safety for nothing.
>>>>
>>>> Konstantin
>>>>
>>>>
>>>> 2014-03-11 5:12 GMT+02:00 Svetkin Mikhail <mikhail.svetkin at gmail.com>:
>>>>
>>>> Explain:
>>>>> I was creating custom widgets with the help of Qt-designer.
>>>>> And I have noticed I have to duplicate my code, if I want to edit
>>>>> properties of the widget in qt-designer property editor.
>>>>> Simple Example:
>>>>>
>>>>>
>>>>> 1. // custom_widget_first.h
>>>>> 2.
>>>>> 3. #include <QWidget>
>>>>> 4. #include <QString>
>>>>> 5. #include <QPaintEvent>
>>>>> 6.
>>>>> 7. class CustomWidgetFirst : public QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> {
>>>>> 8. Q_OBJECT
>>>>> 9. Q_PROPERTY(QString <http://qt-project.org/doc/QString.html> value
>>>>> READ label WRITE setLabel)
>>>>> 10. public:
>>>>> 11. explicit CustomWidgetFirst(QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> *parent = 0)
>>>>> 12. ~CustomWidgetFirst();
>>>>> 13.
>>>>> 14. QString <http://qt-project.org/doc/QString.html> label()
>>>>> const;
>>>>> 15. void setLabel(const QString<http://qt-project.org/doc/QString.html>
>>>>> &label);
>>>>> 16.
>>>>> 17. protected:
>>>>> 18. void paintEvent(QPaintEvent<http://qt-project.org/doc/QPaintEvent.html>
>>>>> *event);
>>>>> 19.
>>>>> 20. private:
>>>>> 21. QString <http://qt-project.org/doc/QString.html> m_label;
>>>>> 22. };
>>>>> 23.
>>>>> 24. // custom_widget_first.cpp
>>>>> 25.
>>>>> 26. #include "custom_widget_first.h"
>>>>> 27.
>>>>> 28. CustomWidgetFirst::CustomWidgetFirst(QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> *parent)
>>>>> 29. : QWidget <http://qt-project.org/doc/QWidget.html>(parent) {
>>>>> 30. }
>>>>> 31.
>>>>> 32. QString <http://qt-project.org/doc/QString.html>
>>>>> CustomWidgetFirst::label() const {
>>>>> 33. return m_label;
>>>>> 34. }
>>>>> 35.
>>>>> 36. void CustomWidgetFirst::setLabel(const QString<http://qt-project.org/doc/QString.html>
>>>>> &label) {
>>>>> 37. m_label = label;
>>>>> 38. }
>>>>> 39.
>>>>> 40. void CustomWidgetFirst::paintEvent(QPaintEvent<http://qt-project.org/doc/QPaintEvent.html>
>>>>> *event) {
>>>>> 41. // some paint
>>>>> 42. }
>>>>> 43.
>>>>> 44. CustomWidgetFirst::~CustomWidgetFirst() {
>>>>> 45. }
>>>>> 46.
>>>>> 47. // custom_widget_second.h
>>>>> 48.
>>>>> 49. #include <QWidget>
>>>>> 50. #include <QString>
>>>>> 51.
>>>>> 52. namespace Ui {
>>>>> 53. class Form;
>>>>> 54. }
>>>>> 55.
>>>>> 56. class CustomWidgetSecond : public QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> {
>>>>> 57. Q_OBJECT
>>>>> 58. Q_PROPERTY(QString <http://qt-project.org/doc/QString.html>
>>>>> text
>>>>> 59. READ getUiCustomWidgetSecondTextLabel
>>>>> 60. WRITE setUiCustomWidgetSecondTextLabel)
>>>>> 61.
>>>>> 62. public:
>>>>> 63. explicit CustomWidgetSecond(QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> *parent = 0)
>>>>> 64. ~CustomWidgetSecond();
>>>>> 65.
>>>>> 66. QString <http://qt-project.org/doc/QString.html>
>>>>> getUiCustomWidgetFirstLabel() const; // dublicate
>>>>> code
>>>>> 67. void setUiCustomWidgetFirstTextLabel(const QString<http://qt-project.org/doc/QString.html>
>>>>> &text); // dublicate code
>>>>> 68.
>>>>> 69. private:
>>>>> 70. Ui::Form *ui; // ui generated from uic and have several
>>>>> widgets, including CustomWidgetFirst
>>>>> 71. };
>>>>> 72.
>>>>> 73. // custom_widget_second.cpp
>>>>> 74.
>>>>> 75. #include "custom_widget_second.h"
>>>>> 76. #include "ui_form.h"
>>>>> 77.
>>>>> 78. CustomWidgetSecond::CustomWidgetSecond(QWidget<http://qt-project.org/doc/QWidget.html>
>>>>> *parent)
>>>>> 79. : QWidget <http://qt-project.org/doc/QWidget.html>(parent),
>>>>> 80. ui(new Ui::Form) {
>>>>> 81. ui->setupUi(this);
>>>>> 82. }
>>>>> 83.
>>>>> 84. QString <http://qt-project.org/doc/QString.html>
>>>>> CustomWidgetSecond::getUiCustomWidgetFirstTextLabel() const { //
>>>>> duplicate code
>>>>> 85. return ui->CustomWidgetFirst->label();
>>>>> // duplicate code
>>>>> 86. }
>>>>> // duplicate code
>>>>> 87.
>>>>> 88. void CustomWidgetSecond::setUiCustomWidgetFirstTextLabel(const
>>>>> QString <http://qt-project.org/doc/QString.html> &text) { //
>>>>> duplicate code
>>>>> 89. ui->CustomWidgetFirst->setLabel(text);
>>>>> // duplicate code
>>>>> 90. }
>>>>> // duplicate code
>>>>> 91.
>>>>> 92. CustomWidgetSecond::~CustomWidgetSecond() {
>>>>> 93. delete ui;
>>>>> 94. }
>>>>>
>>>>>
>>>>> Would suggest to solve this problem in this way(The code marked as
>>>>> duplicate does not need anymore.):
>>>>>
>>>>> 1. Q_PROPERTY(QString <http://qt-project.org/doc/QString.html> label
>>>>> ALIAS CustomWidgetFirst ui->custom_widget_first_obj->value ) //
>>>>> where "value" property name
>>>>>
>>>>> The ALIAS attribute indicates that the property will be reference on
>>>>> another
>>>>> property. If ALIAS property has a signal, you need to declare the same
>>>>> signal
>>>>> because moc will automatically generate connect(aliasObject,
>>>>> aliasSignal, yourClassObject, aliasSignal)
>>>>> and you will only need call initAliasNotify function in the class
>>>>> construct.
>>>>>
>>>>>
>>>>> 2014-03-10 22:43 GMT+06:00 Giuseppe D'Angelo <dangelog at gmail.com>:
>>>>>
>>>>> Can you please explain what this feature is about, why do you think
>>>>>> it's useful, how it's supposed to be used, etc.?
>>>>>>
>>>>>> On 10 March 2014 17:30, mikhail.svetkin at gmail.com
>>>>>> <mikhail.svetkin at gmail.com> wrote:
>>>>>> > Hello, I would like to clarify wherein the complexity
>>>>>> > (https://codereview.qt-project.org/#change,80412)?
>>>>>> > Ready to listen to any suggestions and implement them.
>>>>>> >
>>>>>> > --
>>>>>> > Mikhail Svetkin
>>>>>> > _______________________________________________
>>>>>> > Development mailing list
>>>>>> > Development at qt-project.org
>>>>>> > http://lists.qt-project.org/mailman/listinfo/development
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Giuseppe D'Angelo
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Development mailing list
>>>>> Development at qt-project.org
>>>>> http://lists.qt-project.org/mailman/listinfo/development
>>>>>
>>>>>
>>>>
>>>
>>
>
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