Problem Assigning members to XRC objects
Tim Burgess
Hi,
I’m successfully loading an XRC file that contains subclass entries. The relevant classes contain member variables for elements within the XRC file, such as:
class SampleNotebookPage: public wxPanel
{
wxDECLARE_DYNAMIC_CLASS(SampleNotebookPage);
public:
SampleNotebookPage ();
// Creation
bool Create()
{
tcAttributeValue = XRCCTRL(*this, "AttributeValue", wxTextCtrl);
tcAttributeValue->Connect(wxEVT_TEXT, wxTextEventHandler(EBrailleRequiredMetaPage::OnTextChange));
…
};
~ SampleNotebookPage ();
…
wxTextCtrl * tcAttributeVallue;
}
I successfully initialize such members when I create an instance of the class. However, though the handlers fire correctly, trying to reference one of my member variables within the handler leads to exceptions. Here’s an example:
void EBrailleRequiredMetaPage::OnTextChange(wxCommandEvent& event)
{
int id = event.GetId();
if (id == XRCID("tcAttributeValue"))
{
tcAttributeValue= XRCCTRL(*this, "tcAttributeValue", wxTextCtrl);
// Assertion here:
if (tcAttributeValue->GetValue().Trim().IsEmpty())
{
…
}
else
{
…
}
}
}
If I try to access the member directly:
tcTitle->GetValue();
I get an exception.
What am I missing here, as I thought I was following all of the examples I’ve found.
Many thanks in advance.
Tim
Maarten Bent
Is your example code trying to reference the same object?
Because in the Create function you use the XRC name "AttributeValue", but in the event handler you use XRC name "tcAttributeValue".
Secondly, you use "tcAttributeValue->Connect". I think this is incorrect. You want to Connect to the event handler of your class, not the event handler of tcAttributeValue.
It should be something like:
Connect(tcAttributeValue->GetId(), wxEVT_TEXT, wxTextEventHandler(EBrailleRequiredMetaPage::OnTextChange));
Even better would be to not use the legacy Connect, but instead use Bind. Which likely will warn about this problem at compile-time instead of run-time.
Bind(wxEVT_TEXT, &EBrailleRequiredMetaPage::OnTextChange, this, tcAttributeValue->GetId());
Hope this helps,
Maarten
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Tim Burgess
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