Is there any way to simulate a try-finally
or try-except
in a language that doesn't have them?
If there's some random, unpredictable, exception happens i need to be sure some cleanup runs.
i could try to be sure that no exception in thrown, that way i am sure my cleanup code always runs - but then i wouldn't need the try-finally/except
.
Right this moment i'm trying to create a try-finally
in Lua; but i think any solution would work in other languages as well.
Although, for the life of me, i cannot figure out how an exception can be handled without the plumbing provided by the language infrastructure.
But never hurts to ask.
Lua already has the necessary mechanisms to do something not entirely unlike exceptions. Namely pcall
.
You can use pcall
to execute any Lua function. If that function (or any function it calls) calls error
(assert
calls error
if the assertion condition is not true), then flow control will return to the site of the pcall
statement. The pcall
will return false and an error message (what is passed to error
).
With this, you can "throw" errors and "catch" them. Your "try" is just the pcall
; your "catch" statement is what checks the pcall
result.
Also, remember: Lua is a garbage collected environment. You shouldn't need to do any cleanup work. Or if you do, you need to change whatever Lua module requires it. Lua APIs should be Lua APIs, not C or C++ APIs.