CODEWITHSUNDEEP
c++
Nidhoegger
Nidhoegger

Reputation: 5232

How to return C pointer automatically

I am currently wrapping a library written for C for my C++ program. As to do so I make objects that automatically take care of deleting the C parts when an object goes out of scope. I have done this as an example for an sqlite3_stmt *:

class auto_stmt_t
{
public:
    auto_stmt_t() :
        stmt_(NULL)
    {

    }

    virtual ~auto_stmt_t()
    {
        reset();
    }

    void reset()
    {
        if (stmt_ != NULL)
        {
            ::sqlite3_finalize(stmt_);
            stmt_ = NULL;
        }
    }

    bool prepare(const std::string &query, sqlite3 *db)
    {
        reset();
        return ::sqlite3_prepare_v2(db, query.c_str(), -1, &stmt_, NULL) == SQLITE_OK;
    }

private:
    sqlite3_stmt stmt_;

};

Now I want to pass this object to a sqlite function such as sqlit3_step which takes a sqlite3_stmt * as argument.

Is there a way I can just pass my object which then will get auto castet? Something like this:

auto_stmt_t stmt;
stmt.prepare("SELECT bar FROM foo");
::sqlite3_step(stmt);

I have seen that this is possible, which operator will I need to overload to automatically get the sqlite3_stmt * for this to work?

Upvotes: 1

Views: 112

Answers (2)

Maxim Egorushkin
Maxim Egorushkin

Reputation: 136425

One way is to add a wrapper member function that calls sqlite3_step for you and also checks for errors.

Upvotes: 0

Ted Lyngmo
Ted Lyngmo

Reputation: 117513

Add 

operator sqlite3_stmt* () const { return &stmt_; }

to your wrapper class.

Upvotes: 3

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