"Initialisation of immutable value'context' was never used, consider replacing assignment to '_' or removing it

Question

In swift I declared a variable as

let context:LAContext = LAContext()

It throws a warning

"Initialisation of immutable value'context' was never used, consider replacing assignment to '_' or removing it.

Answer 1

It's all in the error message

value...was never used

Your variable isn't being used anywhere, so Xcode tells you that you can remove it (because having unused variables is a waste of memory). Just use your variable somewhere and the error will go away (e.g. get a value from it, print it, etc).

Of course you mean to use it somewhere right? Otherwise you wouldn't have declared it. It's just that the Xcode (especially the new one, I noticed) checks for errors immediately, so these kinds of errors appear before you can really do anything about it.

Edit: I didn't imagine that almost 7 years later people would still be commenting on a post regarding a beginner-level compiler warning, but to be more specific, yes there are some cases where you might not want to keep a variable around or where you want to discard some return value, so you don't necessarily always "mean to use it somewhere". See comments for more.