Artificial block
Several times, you can limit the lifetime of a local by wrapping the local in an artificial block ({...}). But if for a number of reasons you cannot do that, add a member function that has a similar effect as the destructor. But do not call the destructor itself!
For example, in the case of class File, you might add a close() method. Usually the destructor will simply call this close() method. Note that the close() method will need to mark the File object so a subsequent call won''t re-close an already-closed File. For example it might set the fileHandle_ data member to some nonsensical value like -1, and it might check at the beginning to see if the fileHandle_ is already equal to -1:
class File {
public:
void close();
~File();
...
private:
int fileHandle_; // fileHandle_ >= 0 if/only-if it''s open
};
File::~File()
{
close();
}
void File::close()
{
if (fileHandle_ >= 0) {
...insert code to call the OS to close the file...
fileHandle_ = -1;
}
}
Note that the other File methods may also need to check if the fileHandle_ is -1 (i.e., check if the File is closed). Note also that any constructors that don''t actually open a file should set file Handle_ to -1.