Name followed by :: must be a class or namespace name - c++

Question

I have reviewed numerous articles on this subject both here and elsewhere on the internet and have developed my code to conform with what I've learned. Unfortunately, that doesn't seem to solve this problem. Here are the pieces of the puzzle:
The defined class:
class FileData {
private:
char* filename;
public:
FileData();
void CloseFile(std::fstream file);
int DeleteFile(char* fname);
int FileExist(char* fname);
int OpenDestFile(std::fstream file, char* fname);
int OpenListFile(std::fstream file, char* fname);
int OpenSourceFile(std::fstream file, char* fname);
int ReadBuffer(std::fstream file, char* Buffer);
int ReadListFile(std::fstream file);
int WipeFile(char* fname);
int WriteBuffer(std::fstream file, char* Buffer);
};
The constructor code:
FileData::FileData() : filename(nullptr) {}
The defined function that I'm having an issue with (does not matter which function of the class...they all have the same error):
int FileData::OpenListFile(std::fstream file, char* fname) {
int ccode;
ccode = 0;
file.open(fname, std::fstream::in);
if (file.bad()) {
ccode = -1;
}
return ccode;
}
As a global variable I declare FileRec as an class of FileData:
FileData FileRec;
Here is the actual function call that generates the error:
if ((ccode = FileRec::OpenListFile(&ListFile, fspec3)) != 0) {
// ....
}
Any help would be greatly appreciated. Thanks.

Answer 1

You have declared OpenListFile() as an instance method, not as a static method. FileRec is an instance of the FileData class. You need to use the . operator to access members of an object instance, eg:
FileData FileRec;
std::fstream ListFile;
...
if ((ccode = FileRec.OpenListFile(ListFile, fspec3)) != 0) {
// ...
}
Otherwise, use static for any methods that don't need to access any data members of the FileData class, and then use the class name instead of the instance name when using ::, eg:
class FileData {
public:
static void CloseFile(std::fstream file);
static int DeleteFile(char* fname);
static int FileExist(char* fname);
static int OpenDestFile(std::fstream file, char* fname);
static int OpenListFile(std::fstream file, char* fname);
static int OpenSourceFile(std::fstream file, char* fname);
static int ReadBuffer(std::fstream file, char* Buffer);
static int ReadListFile(std::fstream file);
static int WipeFile(char* fname);
static int WriteBuffer(std::fstream file, char* Buffer);
};
...
int FileData::OpenListFile(std::fstream file, char* fname) {
file.open(fname, std::fstream::in);
return file.bad() ? -1 : 0;
}
...
std::fstream ListFile;
if ((ccode = FileData::OpenListFile(ListFile, fspec3)) != 0) {
// ....
}
That said, note that you can't pass around a std::fstream by value, as std::fstream is not copyable. You need to pass it by reference or by pointer instead:
...
int OpenListFile(std::fstream& file, char* fname);
...
...
int OpenListFile(std::fstream* file, char* fname);
...