Getting value from edit field (C++ WINAPI) - c++

Question

I am writing my first simple program in C++/WINAPI, with a lot of check boxes and a few edit fields, which will set up some calculations on a button press. All of my check boxes work/store info through individual cases, ie
switch (msg)
{
...
case WM_COMMAND:
{
switch (wParam)
{
case IDBC_BoxCheck1:
{...}
case IDBC_BoxCheck2:
{...}
...
} ...
...but I assumed edit fields didn't work as a case statement like a button press, since the value has to be read at the end once it has been changed as many times as the user wants. I looked online and attempted to use the SendMessage(hwnd, ...) and GetWindowText(hwnd, ...) functions to send a WM_GETTEXT command to the edit field and store it to a lpstr string, but I ran into the same problem with both of them - the hwnd for the edit fields aren't declared in the scope where the WM_GETTEXT command is being sent from, and I'm not sure how to get it there. Here is an overview of the structure being used in my program, which comes from a mix of some tutorials I was working with:
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CREATE:
{
return OnCreate(hwnd, reinterpret_cast<CREATESTRUCT*>(lParam));
// OnCreate is a sub function that handles the creation of all the buttons/controls,
// since there are so many of them, with the format:
// HWND editControl1 = CreateControl(...); // CreateControl being another sub fnct
// that creates edit field ctrls
// editControl1 is the hwnd I'm trying
// to read the value from
// HWND checkControl1 = CreateButton(...); // Creates button ctrls, including ck box
...
}
...
case WM_COMMAND:
{
switch (wParam)
{
case IDBC_BoxCheck1: // These control IDs are defined at the top of the file
{
LPSTR Check1;
StoreInfo(Check1); // Just a sub fnct to store info for later calculations
}
case IDBC_BoxCheck2:
{
LPSTR Check2;
StoreInfo(Check2);
} // etc... there are 20 or so check boxes/buttons
case IDBC_Calculate:
{
LPSTR edit1;
GetWindowText(editControl1, edit1, 100); // or SendMessage(editControl1, ...)
// This kicks out the error of editControl1 not being declared in this scope
StoreInfo(edit1);
// Calculation function goes here
} ...
} ....
}
default: DefWindowProc(hwnd, msg, wParam, lParam);
}
}
IDBC_Calculate is the final button pressed before the calculations run. I figured the best place to read and store the values from the edit fields would be after this button is pressed, right before the calculation function is called, but tied to the same command. This is where the hwnd editControl1 is undefined, but I don't know how to send the definition to this scope, or where else I should be reading and storing the edit field values.
Any help or pointers on getting the values from these edit fields to my other functions would be appreciated! I've seen many different ways to check button states in various tutorials/lessons, so I'd love to know if there's a better way to do what I've written above in general.

Answer 1

Your edit fields have IDs right? Then you can use GetDlgItem.
editControl1 = GetDlgItem(hwnd, CONTROL_ID_1);
GetDlgItem is badly named, it doesn't just work in dialog boxes. It gets the handle of any child window from a parent window, using the ID of the child window.
And what Anders K says is correct. The way you are using GetWindowText will crash your program.