The point of using an optional is to signal that the value may be nil and to provide graceful ways of dealing with it if it is
nil. While implicitly unwrapped optionals still provide means of dealing with nil values, they also signal that the value
won’t be nil, and unwrap it automatically. In addition to sending a decidedly mixed signal, this could lead to runtime errors if the
value ever is nil.
It is safest, and clearest to use either an optional or a plain type and avoid the boggy middle ground of implicitly unwrapped optionals.
Noncompliant code example
var greeting : String! // Noncompliant
println(greeting) // At this point the value is nil. Runtime error results
Compliant solution
var greeting : String?
if let howdy = greeting {
println(howdy)
}
