Accessing to a static variable from the same class

Hi,

I'm implementing a class to do operations with a SQLite database and I have this header file

Code:

---

...
class ObjectDatabase{
	public:
		static bool openDatabase(QString);
		static bool createTables();
		static void closeDatabase();
		static bool vacuumDatabase();
		static QString errorString();
	protected:
		static void setErrorString(QString);
	private:
		static QString m_errorString;
};
...

---

But when I try to access from this functions to the var m_errorString the compiler say that the var isn't defined.

What can be the problem?

Thank's

I don't see an error in the code you posted. That means that the error is somewhere else. A typo, perhaps? Maybe your function definition doesn't have "ObjectDatabase::" in front of the name?

If that doesn't help, could you copy/paste the code where you try to access the variable?

Define the static variable in the .cpp file:

Code:

---

QString ObjectDatabase::m_errorString;

---

Oh, you're right. I admit I've never used static variables in C++ in that way. How silly.

So the code that works is this:

objectdatabase.h

Code:

---

...
class ObjectDatabase{
	public:
		static bool openDatabase(QString);
		static bool createTables();
		static void closeDatabase();
		static bool vacuumDatabase();
		static QString errorString();
	protected:
		static void setErrorString(QString);
	private:
		static QString m_errorString;
};
...

---

objectdatabase.cpp

Code:

---

...
QString ObjectDatabase::m_errorString;
...
void ObjectDatabase::setErrorString(QString string){
	m_errorString=string;
}
...

---

Thanks to all

Now we could start a discussion, whether the whole static stuff is good design, or if it is better be done as a singleton. Classes with nothing else but static methods and static members always make me a bit nervous. ;)

You can always convert such class to a namespace with functions and global objects if you don't like a static class :]