How to get a pointer to an instance of a class...
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I'm in a middle of writing my little own framework. I've created a class; lets call it MyFrameWorkApp, and all applications must have one and only one instance of this class (or more likely a class derived from this class). This class should, like in MFC, be instanciated somewhere at global level. (i.e. Before WinMain is called) Then I want WinMain to somehow get a pointer to this instance. This is how MFC does it...
int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
ASSERT(hPrevInstance == NULL);int nReturnCode = -1; CWinThread\* pThread = AfxGetThread(); CWinApp\* pApp = AfxGetApp();.
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.Now, in my case both pThread and pApp points to the CWinApp instance, but that's normal I guess. Later in AfxWinMain, pThread->InitInstance() is called. I want the WinMain-function in my framework to do the same: Get a pointer to the MyFrameWorkApp instance, and call a particilar function. I've tried _lots_ of times to singelstep how MFC does this, my I can't figure it out. Can someone help me? :confused: Sprudling ;)
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I'm in a middle of writing my little own framework. I've created a class; lets call it MyFrameWorkApp, and all applications must have one and only one instance of this class (or more likely a class derived from this class). This class should, like in MFC, be instanciated somewhere at global level. (i.e. Before WinMain is called) Then I want WinMain to somehow get a pointer to this instance. This is how MFC does it...
int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
ASSERT(hPrevInstance == NULL);int nReturnCode = -1; CWinThread\* pThread = AfxGetThread(); CWinApp\* pApp = AfxGetApp();.
.
.Now, in my case both pThread and pApp points to the CWinApp instance, but that's normal I guess. Later in AfxWinMain, pThread->InitInstance() is called. I want the WinMain-function in my framework to do the same: Get a pointer to the MyFrameWorkApp instance, and call a particilar function. I've tried _lots_ of times to singelstep how MFC does this, my I can't figure it out. Can someone help me? :confused: Sprudling ;)
Use a Singleton Class, That will ensure that u can always get the singleton object thru a well known pointer or fn and that it is created only once. regards, Prem
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I'm in a middle of writing my little own framework. I've created a class; lets call it MyFrameWorkApp, and all applications must have one and only one instance of this class (or more likely a class derived from this class). This class should, like in MFC, be instanciated somewhere at global level. (i.e. Before WinMain is called) Then I want WinMain to somehow get a pointer to this instance. This is how MFC does it...
int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
ASSERT(hPrevInstance == NULL);int nReturnCode = -1; CWinThread\* pThread = AfxGetThread(); CWinApp\* pApp = AfxGetApp();.
.
.Now, in my case both pThread and pApp points to the CWinApp instance, but that's normal I guess. Later in AfxWinMain, pThread->InitInstance() is called. I want the WinMain-function in my framework to do the same: Get a pointer to the MyFrameWorkApp instance, and call a particilar function. I've tried _lots_ of times to singelstep how MFC does this, my I can't figure it out. Can someone help me? :confused: Sprudling ;)
Well, trying to copy MFC is fraught with danger and intrigue. MFC tends to do a lot of monkey business behind the scenes. For instance, quite often, instead of calling new, MFC will allocate memory for an object, then call the objects constructor manually. I guess it makes sense if you consider that MFC came from DOS originally, over 10 years ago. Anyways, how MFC does this is hidden in the constructor for CWinApp. In there, They do a few things, such as a module state variable = this (this being the CWinApp object) and doing some asserts that will assert if you try to create more than one instance. This isn't the best way to do this, however. The better way would be to make your MyFrameWorkApp a singleton object, which makes it impossible to create more than one instance. If you don't know what a singleton is, I suggest doing some web searches on it, or buying the most excellent book "Design Patterns". The reason you can't single-step into this is that the CWinApp's constructor get's called *BEFORE* WinMain. You have to put a breakpoint in CWinApp's constructor before you execute the app. -- Where are we going? And why am I in this handbasket?