How to write a cctor and op= for a factory class with ptr to abstract member field?
- by Kache4
I'm extracting files from zip and rar archives into raw buffers. I created the following to wrap minizip and unrarlib:
Archive.hpp
#include "ArchiveBase.hpp"
#include "ArchiveDerived.hpp"
class Archive {
public:
Archive(string path) {
/* logic here to determine type */
switch(type) {
case RAR:
archive_ = new ArchiveRar(path);
break;
case ZIP:
archive_ = new ArchiveZip(path);
break;
case UNKNOWN_ARCHIVE:
throw;
break;
}
}
Archive(Archive& other) {
archive_ = // how do I copy an abstract class?
}
~Archive() { delete archive_; }
void passThrough(ArchiveBase::Data& data) { archive_->passThrough(data); }
Archive& operator = (Archive& other) {
if (this == &other) return *this;
ArchiveBase* newArchive = // can't instantiate....
delete archive_;
archive_ = newArchive;
return *this;
}
private:
ArchiveBase* archive_;
}
ArchiveBase.hpp
class ArchiveBase {
public:
// Is there any way to put this struct in Archive instead,
// so that outside classes instantiating one could use
// Archive::Data instead of ArchiveBase::Data?
struct Data {
int field;
};
virtual void passThrough(Data& data) = 0;
/* more methods */
}
ArchiveDerived.hpp "Derived" being "Zip" or "Rar"
#include "ArchiveBase.hpp"
class ArchiveDerived : public ArchiveBase {
public:
ArchiveDerived(string path);
void passThrough(ArchiveBase::Data& data);
private:
/* fields needed by minizip/unrarlib */
// example zip:
unzFile zipFile_;
// example rar:
RARHANDLE rarFile_;
}
ArchiveDerived.cpp
#include "ArchiveDerived.hpp"
ArchiveDerived::ArchiveDerived(string path) { //implement }
ArchiveDerived::passThrough(ArchiveBase::Data& data) { //implement }
Somebody had suggested I use this design so that I could do:
Archive archiveFile(pathToZipOrRar);
archiveFile.passThrough(extractParams); // yay polymorphism!
How do I write a cctor for Archive?
What about op= for Archive?
What can I do about "renaming" ArchiveBase::Data to Archive::Data? (Both minizip and unrarlib use such structs for input and output. Data is generic for Zip & Rar and later is used to create the respective library's struct.)
