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Should I check QEvent dynamic_cast result if I already checked event->type()?
0
QEvent has a type() member function which returns the event type as enum value. Should I check dynamic_cast result for QEvent* if I already checked event->type(). E.g.
bool ClassName::eventFilter(QObject* obj, QEvent* event)
{
if (event->type() == QEvent::KeyPress)
{
auto ke = dynamic_cast<QKeyEvent*>(event);
if (ke) // <----------- needed?
{
// ...
}
}
// ...
}
Is if (ke) condition needed here?
c++ qt qevent
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
add a comment |
0
QEvent has a type() member function which returns the event type as enum value. Should I check dynamic_cast result for QEvent* if I already checked event->type(). E.g.
bool ClassName::eventFilter(QObject* obj, QEvent* event)
{
if (event->type() == QEvent::KeyPress)
{
auto ke = dynamic_cast<QKeyEvent*>(event);
if (ke) // <----------- needed?
{
// ...
}
}
// ...
}
Is if (ke) condition needed here?
c++ qt qevent
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
1
If you already know the type you can safely usestatic_castinstead without checking the result against null pointer. This is faster approach.
– vahancho
Nov 21 '18 at 14:17
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
1
That's what I meant. Andstatic_castis more preferable in this case.
– vahancho
Nov 21 '18 at 14:29
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
Have a look at Qt doc.: Event Filters. There you find an example which uses astatic_castlike mentioned by @vahancho.
– Scheff
Nov 21 '18 at 15:16
add a comment |
0
0
0
QEvent has a type() member function which returns the event type as enum value. Should I check dynamic_cast result for QEvent* if I already checked event->type(). E.g.
bool ClassName::eventFilter(QObject* obj, QEvent* event)
{
if (event->type() == QEvent::KeyPress)
{
auto ke = dynamic_cast<QKeyEvent*>(event);
if (ke) // <----------- needed?
{
// ...
}
}
// ...
}
Is if (ke) condition needed here?
c++ qt qevent
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
QEvent has a type() member function which returns the event type as enum value. Should I check dynamic_cast result for QEvent* if I already checked event->type(). E.g.
bool ClassName::eventFilter(QObject* obj, QEvent* event)
{
if (event->type() == QEvent::KeyPress)
{
auto ke = dynamic_cast<QKeyEvent*>(event);
if (ke) // <----------- needed?
{
// ...
}
}
// ...
}
Is if (ke) condition needed here?
c++ qt qevent
c++ qt qevent
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
asked Nov 21 '18 at 14:09
αλεχολυταλεχολυτ
1,95411546
1,95411546
1
If you already know the type you can safely usestatic_castinstead without checking the result against null pointer. This is faster approach.
– vahancho
Nov 21 '18 at 14:17
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
1
That's what I meant. Andstatic_castis more preferable in this case.
– vahancho
Nov 21 '18 at 14:29
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
Have a look at Qt doc.: Event Filters. There you find an example which uses astatic_castlike mentioned by @vahancho.
– Scheff
Nov 21 '18 at 15:16
add a comment |
1
If you already know the type you can safely usestatic_castinstead without checking the result against null pointer. This is faster approach.
– vahancho
Nov 21 '18 at 14:17
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
1
That's what I meant. Andstatic_castis more preferable in this case.
– vahancho
Nov 21 '18 at 14:29
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
Have a look at Qt doc.: Event Filters. There you find an example which uses astatic_castlike mentioned by @vahancho.
– Scheff
Nov 21 '18 at 15:16
1
1
If you already know the type you can safely use
static_cast instead without checking the result against null pointer. This is faster approach.– vahancho
Nov 21 '18 at 14:17
If you already know the type you can safely use
static_cast instead without checking the result against null pointer. This is faster approach.– vahancho
Nov 21 '18 at 14:17
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
1
1
That's what I meant. And
static_cast is more preferable in this case.– vahancho
Nov 21 '18 at 14:29
That's what I meant. And
static_cast is more preferable in this case.– vahancho
Nov 21 '18 at 14:29
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
Have a look at Qt doc.: Event Filters. There you find an example which uses a
static_cast like mentioned by @vahancho.– Scheff
Nov 21 '18 at 15:16
Have a look at Qt doc.: Event Filters. There you find an example which uses a
static_cast like mentioned by @vahancho.– Scheff
Nov 21 '18 at 15:16
add a comment |
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1
If you already know the type you can safely use
static_castinstead without checking the result against null pointer. This is faster approach.– vahancho
Nov 21 '18 at 14:17
@vahancho hence second checking is redundant, right?
– αλεχολυτ
Nov 21 '18 at 14:24
1
That's what I meant. And
static_castis more preferable in this case.– vahancho
Nov 21 '18 at 14:29
@vahancho maybe some reference to Qt documentation/implementation? Such info should be placed in answer area and accepted :)
– αλεχολυτ
Nov 21 '18 at 14:34
Have a look at Qt doc.: Event Filters. There you find an example which uses a
static_castlike mentioned by @vahancho.– Scheff
Nov 21 '18 at 15:16