Three questions used in Swift

  1. (Ternary, Conditional, Operator)
    , which is more common in most languages.
    Boolean value “true”: “false””
  2. Optional values,
    optional values, and yes, a pair. ? in behind a certain type, can be, this value is not too sure if this type is, if not to a nil of it;! Can be understood as, must give a type I, or Lao Tzu minutes to hang you see. ?
  3. Null operator (Nil, Coalescing, Operator)?
    ? I haven’t seen it in other languages. E? F is equivalent to e = = nil = e: F, optional type E is not nil, e, otherwise F.
Var e: String? Var f = "fuck" e?? f / `e! = nil? E!: f`, optional type `e` is not `nil`, `e, `f`, or else. (pay attention to the space before and after)