Problems accessing static member variable from static member function

[montylee]

this looks ok, but when you define QComboBox like static class member you didn't set a parent. so when you start application you will see this combobox like separate widget. so, you must reparent combobox in this case. anyway, I suggest you refuse this approach.

no, my code is working fine. I have a separate combo box member variable which is actually displayed on the GUI. The static variable is just used as i require to pass the address of the variable to a different class through a static function. Since a static member function can only access static member variables, so i had to use an extra variable...

in the class constructor, i just assign the normal combo box pointer to the static combo box variable...in the GUI, the normal combo box is displayed.

[spirit]

I guess it works fine, because you use layouts.

[montylee]

yes i am using layouts but as i said the combo box being shown on the GUI is a normal member variable.
The static variable just stores the same address as the normal variable...so it's just a copy...

Thanks for your help!

[spirit]

in the class constructor, i just assign the normal combo box pointer to the static combo box variable....

this can lead to memory leak, because when you init static variable you create a new comboboex and then (according to your words) you reset variable with a new object, but don't destroy old.

[montylee]

i am not allocating new memory for the static combo box, i am just assigning the same address to the static variable, so there is no extra memory allocation. Here's my code:

sm_pTestCombo = m_pTestCombo;

sm_pTestCombo = m_pTestCombo;

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here, sm_pTestCombo is the static member variable and m_pTestCombo is the normal member variable.

[spirit]

what about this

QComboBox *Test::m_comboBox = new QComboBox();

QComboBox *Test::m_comboBox = new QComboBox();

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?

[spirit]

if you use code like this

QComboBox *Test::m_comboBox = 0;

QComboBox *Test::m_comboBox = 0;

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then ok.

[montylee]

i think that code was posted by you. I am not allocating any new memory

[Sandip]

Hi,

You can try a different solution.
Let's see it is easy and safe also.

class GetComboInstance
{
public:
static GetComboInstance* createInstance();
updateCombo();
private:
QComboBox *m_pComboBox;
static GetComboInstance *m_pInstance;
};

In Cpp file:

static GetComboInstance *GetComboInstance::m_pInstance = NULL;
static GetComboInstance* GetComboInstance::createInstance()
{
if(m_pInstance == NULL)
{
m_pInstance = new GetComboInstance();
}
return m_pInstance;
}

now you can call updateCombo method on your instance of GetComboInstance class from any class. It is better and safe way.

[Sandip]

Please let me know what do you think

[Kumosan]

I think that when you describe the singleton pattern, you should do it right, e.g. make constructors protected or private. ;-)

http://www.inquiry.com/techtips/cpp_.../10min0200.asp