CListBoxGetItemDataPtr and dynamic cast
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From: Vaclav on 1 Dec 2007 06:37 Hello, I am trying to get a pointer stored in a CListBox item. int li_index = m_lineTypesListBox.GetCurSel(); if (LB_ERR == li_index) { return 0; } void* pItem = m_lineTypesListBox.GetItemDataPtr(li_index); QLin* pLin = dynamic_cast<QLin*>(pItem); Getting error C2681: 'void *' : invalid expression type for dynamic_cast Thanks Vaclav
From: Tom Serface on 1 Dec 2007 11:54 I'm guessing that you're getting this error since the listbox is returning a void * which is not related to a QLin *. I would try reinterpret_cast or just saying QLin* pLin = (QLin*)pItem; Tom "Vaclav" <vjedlicka(a)atlas.cz> wrote in message news:uB1TA6ANIHA.4880(a)TK2MSFTNGP03.phx.gbl... > Hello, > > I am trying to get a pointer stored in a CListBox item. > > > int li_index = m_lineTypesListBox.GetCurSel(); > if (LB_ERR == li_index) > { > return 0; > } > > void* pItem = m_lineTypesListBox.GetItemDataPtr(li_index); > QLin* pLin = dynamic_cast<QLin*>(pItem); > > > Getting > error C2681: 'void *' : invalid expression type for dynamic_cast > > > Thanks > Vaclav >
From: Giovanni Dicanio on 1 Dec 2007 11:57 "Vaclav" <vjedlicka(a)atlas.cz> ha scritto nel messaggio news:uB1TA6ANIHA.4880(a)TK2MSFTNGP03.phx.gbl... > I am trying to get a pointer stored in a CListBox item. > void* pItem = m_lineTypesListBox.GetItemDataPtr(li_index); > QLin* pLin = dynamic_cast<QLin*>(pItem); You might want to use a C++ reinterpret_cast, or just C-style casts, e.g.: QLin * pLin = reinterpret_cast<QLin*>( pItem ); or QLin * pLin = (QLin *)pItem; G
From: Giovanni Dicanio on 1 Dec 2007 12:06 Ops, Tom: sorry if I answered again... (Your post did not appear on my Outlook when I sent mine) G "Tom Serface" <tom.nospam(a)camaswood.com> ha scritto nel messaggio news:1522916F-602D-4ED7-96A2-5EBF78CF9D4A(a)microsoft.com... > I'm guessing that you're getting this error since the listbox is returning > a void * which is not related to a QLin *. I would try reinterpret_cast > or just saying > > QLin* pLin = (QLin*)pItem; > > Tom > > "Vaclav" <vjedlicka(a)atlas.cz> wrote in message > news:uB1TA6ANIHA.4880(a)TK2MSFTNGP03.phx.gbl... >> Hello, >> >> I am trying to get a pointer stored in a CListBox item. >> >> >> int li_index = m_lineTypesListBox.GetCurSel(); >> if (LB_ERR == li_index) >> { >> return 0; >> } >> >> void* pItem = m_lineTypesListBox.GetItemDataPtr(li_index); >> QLin* pLin = dynamic_cast<QLin*>(pItem); >> >> >> Getting >> error C2681: 'void *' : invalid expression type for dynamic_cast >> >> >> Thanks >> Vaclav >> >
From: Joseph M. Newcomer on 1 Dec 2007 21:40
Typically, I just subclass the listbox and create a method QLin * GetItemDataPtr(int n) { return (QLin*)CListBox::GetItemDataptr(n); } It probably would have been better if these methods had been virtual, but in the interest of "efficiency" they are not. I see no reason to have stored it in a void *. joe On Sat, 1 Dec 2007 12:37:08 +0100, "Vaclav" <vjedlicka(a)atlas.cz> wrote: >Hello, > >I am trying to get a pointer stored in a CListBox item. > > > int li_index = m_lineTypesListBox.GetCurSel(); > if (LB_ERR == li_index) > { > return 0; > } > > void* pItem = m_lineTypesListBox.GetItemDataPtr(li_index); > QLin* pLin = dynamic_cast<QLin*>(pItem); > > >Getting >error C2681: 'void *' : invalid expression type for dynamic_cast > > >Thanks >Vaclav > Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm |