Hi Daniel,
This won't work. Let's say there has been two keypresses and I called
handleKey two times. First time it updates the `dat` and returns it
but how can I pass that updated `dat` object to the same function in
second invocation?
---
Ömer Sinan Ağacan
http://osa1.net
2014-03-02 23:38 GMT+02:00 Daniel Trstenjak
Hi Ömer,
In a sense I'm like trying to emulate something like closures with mutable closed-over data in impure languages.
One way is to keep the specific data completely out of the Widget and use a closure to hold the data:
data Widget = Widget { handleKey :: Key -> Widget , draw :: Int -> Int -> Int -> Int -> IO () , getFocus :: Widget , loseFocus :: Widget }
someWidget :: SomeWidgetData -> Widget someWidget dat = Widget { handleKey = \key -> case key of 'A' -> someWidget $ dat { ... } ; ... , draw = \x y w h -> ... , getFocus = someWidget $ dat { focus = True } , loseFocus = someWidget $ dat { focus = False } }
Greetings, Daniel _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe