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- Subject: Re: Guessing the expected result type from an __index function
- From: Jerome Vuarand <jerome.vuarand@...>
- Date: Mon, 13 May 2013 08:38:22 +0100
2013/5/12 Jean-Luc Jumpertz <email@example.com>:
> And it would be much better if some type of hint about the foreseeable usage of a field could be passed as an extra parameter to the index metamethod in a future version of Lua. This would allow the index metamethod to return different (but related) data for a same key depending of the field expected usage.
> What do you think of it?
You don't always know at index time how the returned value will be
used. Consider for example:
local obj = get_one_of_your_objects()
local save = obj.save
--[[ do a lot of stuff here ]]
if some_unpredictable_result then
save(obj) -- call method
print(save) -- use property value
With your hack, it's no longer possible to call the method in that way
(which I admit is very unusual).
I don't know ObjectiveC, but from your description there doesn't seem
to be any perfect solution. IMHO you should keep using the objc
introspection mechanism you mention in the __index metamethod to
distinguish between properties and methods, and provide a fallback
mechanism for when it's not properly registered by the third party
object author (for example provide two functions
objc.get_property(obj, name) and objc.get_method(obj, name) in your