Say I have an array, [1,2,3,4] and want to use parallel assignment to assign a to 1 and b to 3. I figured I could do something like:
a, _, b, _ = [1,2,3,4]
or even omit the last _ and it will work but Ruby will produce warnings for this for unused variables. Is there some other way to do this? Is this way of using underscores recommended?
There should not be any warning about unused variables, provided of course that you actually use a and b somewhere. Using _ in this way is recommended and idiomatic, and even officially supported by the interpreter in that it actually does not generate warnings for unused variables if the name of the variable is _ or starts with _.
The warning is about unused variables a and b, not about _. An alternative :
a, b = [1,2,3,4].values_at(0,2)
values_at is my preferred way of doing/seeing it. It's a lot easier to figure out what elements are being retrieved and assigned. Using _ works but we're left having to figure out which variables are assigned which elements when reading it.