It seems Optional.map() when the transform closure returns nil, then result is Optional(nil) , which is same as Optional.some(nil)? Still a nil but is wrap up an optional? But Optional.flatMap() when the transform closure returns nil, the result is just nil, which is simpler. Why not just always use flatMap, I want to ask?
There must be reason we have both Optional.map() and Optional.flatMap()? Any good explanation?
let anOptional: Int? = 123
let aNilValue: Int? = nil
// Trailing closure in this context is confusable with the body of the statement; pass as a parenthesized argument to silence this warning
let g = anOptional.map {_ in aNilValue }
print("optional.map returns: \(g)")
//prints: optional.map returns: Optional(nil)
let h = anOptional.flatMap {_ in aNilValue }
print("optional.flatMap returns: \(h)")
//prints: optional.flatMap returns: nil