On Sun, 2004-11-14 at 18:08 -0800, Cory Nelson wrote:
boost.variant :)
Possible. Let me expand my example. The Data class is really the mechanism I want to use to pass data between Components. A Component is a virtual class that is inherited by classes that implement the Component interface. Each Component class performs a action (e.g. Detect file type) when the function process() is called and returns the results (e.g. Data<string>) when the outcome() function is called. These two functions are called by a visitor which walks the graph of Component objects. A simple graph example is: A --> B --> ... The Component 'A' performs an action which generates a 'std::string' as a result. When the graph visitor calls A.process() then this result is stored in the A class object. The graph visitor takes the result via outcome as a Datastd::string and initializes B.init (Datastd::string). The visitor continues on until the end. Here is how I am defining the Component class: class Component { public: // Boost::variant? - need to store multiple types in m_data void init (uint32_t id, Data<...> data); // run child class action (call process) void run (void); // Virtual function child class must support. Using input stored in // m_data do some action and store the result internally. virtual void process (void) = 0; // get child results // Boost::variant? - need to return the results. The return type is // dependent on the child class's function. In 'A' the return type is // a std::string. Call outcome() in child Data<...> result (void); // Virtual function child class must support. return results virtual Data<...> outcome (void) = 0; private: // Boost::variant? - need to store // multiple types of inputs maybe here depending on the child class's // function. For example, 'A' needs a 'unsigned int' and 'std::string' // to work. std::list< Data<...> > m_data; }; So input Data element types (e.g. int, std::string) depend on the output of the previous Component in the graph connected to the present Component. The output Data element type (e.g. int, std::string) depends on the implementation of the child class, e.g. result of process() retrieved by calling outcome(). I think the boost::variant might work. I want to see if this further detailing of the example help to confirm this. Stephen