[Solved] How to subclass QLineEdit
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Hi All,
I would like to Subclass QLineEdit so that it has a signal that returns a pointer to the QLineEdit itself.
I have a lot of QLineEdit that are connected using a loop. However, right now I am using a signalMapper to pass the QLineEdit ID to a slot. Using a direct pointer would be a lot easier and cleaner and provide easy access to all class.
Could you help me build a simple implementation of that?
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and about which signal you are talking about?
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I would build MyLineEdit class
@#ifndef MYLINEEDIT_H
#define MYLINEEDIT_H#include <QWidget>
#include <QLineEdit>class MyLineEdit : public QLineEdit
{
Q_OBJECT
public:
explicit MyLineEdit(const QString & contents, QWidget * parent = 0);signals:
void output( QLineEdit* currentLineEdit);public slots:
void textChanged(const QString & contents);};
#endif // MYLINEEDIT_H
@@#include "mylineedit.h"
MyLineEdit::MyLineEdit(const QString &contents, QWidget *parent) :
QLineEdit(parent)
{
unsigned int test;
test=1;
}void MyLineEdit::textChanged(const QString &contents){
emit output( CurrentLineEdit );
}@
The question would bo how to get the CurrentLineEdit pointer from the class itself.. I don't think it is possible is it?
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bq.
I would like to Subclass QLineEdit so that it has a signal that returns a pointer to the QLineEdit itself.the signal's receiver always can get the sender as QObject*, so I think no need for such signal
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you are thinking to complicated ;)
Is something like this what you want?
@
class MyLineEdit : public QLineEdit
{
Q_OBJECT
public:
explicit MyLineEdit(const QString & contents, QWidget * parent = 0);signals:
void textChanged( QLineEdit*, cosnt QString &);protected slots:
void onTextChanged(const QString & contents);
};
@@
MyLineEdit::MyLineEdit(const QString &contents, QWidget *parent) :
QLineEdit(parent)
{
connect(this SIGNAL(textChanged(const QString &)), this, SLOT(onTextChanged(const QString &)));
}void MyLineEdit::onTextChanged(const QString &contents)
{
emit textChanged( this, contents );
}
@ -
[quote author="NicuPopescu" date="1381493320"]
the signal's receiver always can get the sender as QObject*, so I think no need for such signal[/quote]
i would avoid using sender() in any case, since it breaks OOP concept and you also can't use it in queued connections. -
bq. and you also can’t use it in queued connections
have you tested?
bq. Qt::AutoConnection 0 (default) If the signal is emitted from a different thread than the receiving object, the signal is queued, behaving as Qt::QueuedConnection. Otherwise, the slot is invoked directly, behaving as Qt::DirectConnection. The type of connection is determined when the signal is emitted.
bq. Warning: As mentioned above, the return value of this function is not valid when the slot is called via a Qt::DirectConnection from a thread different from this object's thread. Do not use this function in this type of scenario.
so, as far as I understand with Qt::AutoConnection always will work ... is there a warning for using from a different thread with Qt::DirectConnection, which is not default ...
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[quote author="bareil76" date="1381493753"]
However, you define @void textChanged( QLineEdit*, cosnt QString &);@
with 2 arguments and you connect only the QString??[/quote]
Yes i define the textChanged signal with 2 arguments. The one with 1 argument is still available from the QLineEdit base class. Thus it's a different signal, since the signature is different.[quote author="NicuPopescu" date="1381494337"]
have you tested?[/quote]
you can do it if you don't believe it ;)
I know that it won't work.
In the queued connection an event - containing the parameters as copy - is generated which calls the slot. So there definitely happens a decoupling of the sender.
