Earlier quoted context omitted.
Think the ternary operator, but worse. In Swift, this is expressed by "??". It means "If the previous test returns nil, then execute what is after the ??". For example, if you have a concrete Int, but the source might be an optional, then you could do something like this: let a = b ?? 0 That means that if b is nil, then set a to 0. Otherwise, set it to whatever value b has. You can chain these, like so: let b: Int? =…
In Objective-C (and some other languages with ternary operators) the same can be written like this: int a = b ?: c ?: 0
I hate it when things like this get names that everyone's supposed to know and it's considered a mark against you if you've never heard it before, but I do think the name Elvis Operator is hilarious. :D