Reflection: Casting NewInstance() automagically
Monkey Forums/Monkey Programming/Reflection: Casting NewInstance() automagically
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Is it possible to cast a NewInstance() object to the actual class in question using reflection? For example I was hoping the following would be possible...Local newInstance:= currentClassInfo.Name( currentClassInfo.NewInstance() ) ...but obviously ClassInfo.Name() doesn't work for such purposes. I could really do with creating instances of classes, the class name of which is not precisely known (ie it could be one of many classes, far too many for a Select...Case) until runtime. |
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| Its been a long time since I used reflection , I dont think you can, if you explained why you need to do this other suggestions could be made. creating a new instance may return an 'Object' but it is still the class that you want 'underneath' |
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| Yeah I suspect you're right that it can't be approached this way. I'm trying to get at newInstance.whateverMethod() and I'm doing it via Invoke at the moment (like this), I was just wondering if it was possible to re-factor what I have to something along the lines of what I posted. No real biggie if not. creating a new instance may return an 'Object' but it is still the class that you want 'underneath' It's the 'underneath' bit that's the problem because if you go... Local newInstance:=currentClassInfo.NewInstance() ...then go... newInstance.definiteClassMethod() ...you will get an error that the identifier of your method can't be found. And if you go... Local newInstance:definiteClass=currentClassInfo.NewInstance() ...you'll get an conversion error from object to definiteClass. You have to cast the return from NewInstance() -- ie newInstance:=definiteClass(currentClassInfo.NewInstance()) -- if you want to then go newInstance.definiteClassMethod() So yes, the new instance is the right class "underneath", but that's not very useful* if your code can't determine the class to cast it to via reflection. I think I'm stuck with the "longhand" (Invoke) approach. *In my very particular situation, where I know the method name (because it is shared) but not the exact class name. EDIT: Edited to make a bit more sense :) |
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| yes pretty much if you knew an object that they inherit from you could use that e.g. you want to create a new instance of a car, but it could be any kind of 'vehicle' and vehicle has a method called move_forward so you cast the newinstance to vehicle instead of car. |
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| Cheers Slenkar -- I just spent some time faffing around and realised the same (then rushed back here to post "Aha!") but I could so easily have missed it that I'm very thankful. I will add that the base class needs to define everything you want to access in the extended classes -- that seems to be what was tripping me up previously. Fortunately I don't need my extended classes to do anything unpredictable (I'm fudging function pointers if you hadn't guessed!) so that's me sorted :) |
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