data Renderer = Renderer {destroy :: IO (); render :: SystemOutput -> IO ()}
newtype Initializer = Initializer {initialize :: IO Renderer}
Отправлено с iPad
03.09.2011, в 14:15, "M. George Hansen"
Greetings,
I'm a Python programmer who is relatively new to Haskell, so go easy on me :)
I have a program that uses (or will use) plugins to render output to the user in a generic way. I'm basing the design of the plugin infrastructure on the Plugins library, and have the following interface:
data Renderer = Renderer { initialize :: IO (), destroy :: IO (), render :: SystemOutput -> IO () }
The program loads plugins at the start and runs the initialize function, and then enters the main loop where it repeatedly calls the render function with output to display. When the program exits the main loop, it calls the destroy function to clean up any resources used by the plugin. You can probably already see my problem: how do I pass initialization information created in the initialize function to the render function?
I'm vaguely aware of some solutions to the typical "configuration problem", such as implicit arguments or explicitly passing the configuration data through the function call hierarchy. As far as I can tell, neither of these approaches would work because the program can't know at compile time what, if any, configuration data is used by the plugin.
I suppose I could pass a Dynamic up the call chain and let the plugin decode it in the render function, but that seems a little kludgy to me.
Any thoughts would be greatly appreciated.
-- M. George Hansen
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