Instance

How to use a MongoDB C++ Driver instance.

Initialize the C++ Driver

Basic Usage

void example() {
    // Do not use mongocxx library interfaces at this point!
 
    {
        // Initialize the MongoDB C++ Driver by constructing the instance object.
        mongocxx::instance instance;
 
        // Use mongocxx library interfaces at this point.
        use(mongocxx::client{});
 
        // Cleanup the MongoDB C++ Driver by destroying the instance object.
    }
 
    // Do not use mongocxx library interfaces at this point!
}

Errors

Instance Recreation

void example() {
    {
        mongocxx::instance instance;
 
        try {
            mongocxx::instance another_instance; // Throws.
 
            EXPECT(false && "should not reach this point");
        } catch (mongocxx::exception const& ex) {
            EXPECT(ex.code() == mongocxx::error_code::k_cannot_recreate_instance);
        }
    }
}

Destroyed Instance

void example() {
    // Initialize and cleanup.
    {
        mongocxx::instance instance;
    }
 
    try {
        mongocxx::instance instance; // Throws.
 
        EXPECT(false && "should not reach this point");
    } catch (mongocxx::exception const& ex) {
        EXPECT(ex.code() == mongocxx::error_code::k_cannot_recreate_instance);
    }
 
    try {
        mongocxx::instance instance; // Throws.
 
        EXPECT(false && "should not reach this point");
    } catch (mongocxx::exception const& ex) {
        EXPECT(ex.code() == mongocxx::error_code::k_cannot_recreate_instance);
    }
}