Returning static variable throws error in Visual studio

Question

Returning or accessing a static variable inside a static function throws an error in Visual Studio:

// H File
class LayoutManager : public QObject
{
    static int Access_Data();
    static int data;
};

// CPP

static int data= 0; // Global scope

int LayoutManager::Access_Data()
{
    data= data+ 1;
    return data;
}

Error: Error    LNK2001 unresolved external symbol "public: static int LayoutManager::data" (?mm@LayoutManager@@2HA)

After changing to int LayoutManager::data = 0 in C++, the error is gone, but while assigning a new value to data in another class, it throws a new error:

void MyLayout::Update( void )
{
    LayoutManager::data = 1;  // error here

Please don't edit answers into your question, if the answer didn't solve your problem add a comment to the answer. If you have a new question raise a new question — Alan Birtles, Nov 04 '20 at 07:37

score 1 · Answer 1 · answered Nov 04 '20 at 06:46

Try this

int LayoutManager::data = 0;

This tells the compiler that you mean the data variable in the LayoutManager class and not a regular global variable outside of any class.

It's also an error to repeat the static keyword. The compiler already knows the variable is static from the declaration.

Returning static variable throws error in Visual studio

1 Answers1