How to assign a textbox control in cpp?

[xarzu]

I have a silverlight app that uses TextBox XAML controls.

In the c++ code-behind, IXRTextBoxPtr types are associated with these textboxes using "FindName" like this:

FindName(L"ColNum3", &m_pColNum3);

(where ColNum3 corresponds with the XAML CODE like this: )

Then, the code assigns the pointer like this:

std::wstring wsTransfer; // gets the wstring from imput
const WCHAR * wpszInput;
wpszInput = wsTransfer.c_str();
m_pColNum3->SetText(wpszInput);
but the display does not show the text data.

What am I missing? What steps am I missing to have this text modification display on the screen?

If I did not ask this question completely or left something off, please let me know.

[weaknessforcats]

I don't see where it gets the text either.

This code:

std::wstring wsTransfer;  // gets the wstring from imput
 

creates a wstring object named wsTransfer using the default constructor of wstring--which does not get text.

Then I see:

const WCHAR * wpszInput;
 wpszInput = wsTransfer.c_str();

This fetches the contents of wsTransfer as a C-style string.

This code:

m_pColNum3->SetText(wpszInput); 

sets the address of the text into m_pColNUm3.

Nowhere do I see text values.

[xarzu]

I left out all the details but it gets it.

HRESULT StatsGridControl::SetParsedBoreData(std::vector<st d::vector<std::wstring>> m_vTargetWStringBoreData, std::vector<vPoint5> m_vTargetBoreData)
{
HRESULT hr = S_OK;

std::wstring wsTransfer;
const WCHAR * wpszInput;

for (int iRow = 0; iRow < 4; iRow++)
{
for (int iCol = 0; iCol < 6; iCol++)
{
wsTransfer = m_vTargetWStringBoreData.at(iRow).at(iCol);
wpszInput = wsTransfer.c_str();
switch (iRow)
{
case 0:
if (iCol == 0)
hr = m_pColNum->SetText(wpszInput); // <TextBox x:Name="ColNum">

[weaknessforcats]

This code:

wsTransfer = m_vTargetWStringBoreData.at(iRow).at(iCol);
 wpszInput = wsTransfer.c_str();

retrieves the address of the contents of wsTransfer.

This address is used in:

hr = m_pColNum->SetText(wpszInput); // <TextBox x:Name="ColNum"> 

Now m_pColNum points to an object that now contains the address of the contents. Unless you can peer into SetText aonc confirm it makes a copy of the text, you have a situation where wsTransfer has gone out of scope and its contents destroyed by its destructor. That leaves the objctec pointed at by m_pColNUm with a address that may or may not work depending upon conditions in memory when you finally get around to displaying the text.

The single most dangerous thing you can do in a C++ program is pass pointers around. C++ is not like C. In C YOU control when the pointer is valid. In C++ the compiler controls it.

The first thing I would do is get out my debugger and step through this code.

The second thing would be to make a copy of the data pointed at by wpszInput. So I could insure the data is there when I need it later.

The third thing would be to install a managed pointer for wpszInput.