Setting Object Data *double* For Class ComboBox :: MFC

[kuphryn]

Hi.

I have a CComboBox object. I need to set one or more of its strings to represent a *double* data type. For example:

CComboBox mCbbCandy;

mCbbCandy.Create(WS_CHILD | WS_VISIBLE | WS_BORDER | LBS_NOTIFY | WS_VSCROLL | CBS_DROPDOWNLIST | CBS_SORT, CRect(CPoint(270, 10), CSize(100, 100)), this, IDC_CBB_FLAVORS);

// Setting its value
int i = mCbbCandy.AddString("X");
mCbbCandy.SetItemData(i, 1.99); // $1.99

// Retrieving its value

int i = mCbbCandy.GetCurSel();
double price = mCbbCandy.GetItemData(i);

-----

For some reason, the price does not come out right if I use the decimal point. For example, any whole number works, but not decimal. 

How do you set the item data to a double type? Visual C++ gave warnings about data loss because the CComboBox object expected a DWORD instead of a double.

Thanks,
Kuphryn

 

[javathehut]

just insert the number as a string:

TCHAR szNumber[10] = {0};

wsprintf(szNumber, "%f", 1.99);
mCbbCandy.AddString(szNumber);

The function you were using SetItemData, is used to set a pointer for reference (kind of like the lparam in tree/list views) so its not at all meant to set the value of the combo box item. Hope that helps

 

[Adrian Tung]

javathehut's suggestion will work *unless* you want what the combo box to display to be different from the data that you retrieve from it. If so, you can do a little hack to get your data stored and retrieved properly:

Do a memcpy to copy your float to a DWORD variable, then use SetItemData to store your DWORD. When you need to retrieve the float, do the opposite - use GetItemData to get the DWORD, then memcpy it back to the float. Both DWORD and float are 4 bytes, so memcpy will work.


Hope that helps,
🙂atwl


Edit:
Ignore my first suggestion, I just realized you want a double, not a float. A double is 8 bytes, so there's nothing that you can do except for javathehut's suggestion. Unless you use a pointer to a structure/array/list that stores your double, that is.

 

[kuphryn]

Thanks.

A member brought up another innovative way to get around it without using pointer because you have to clean up all the pointers after the box is closed.

The new technique involves using a container (vector) that mirrors the combobox data.

Here is the post:

http://www.codeproject.com/script/comments/forums.asp?forumid=1647&select=138924#xx138924xx

Kuphryn