This answer is in response to the question in the title, “Shouldn’t Optional be Serializable?” The short answer is that the Java Lambda (JSR-335) expert group considered and rejected it. That note, and this one and this one indicate that the primary design goal for Optional is to be used as the return value of … Read more
If you are using Java 9+, you can use ifPresentOrElse() method: opt.ifPresentOrElse( value -> System.out.println(“Found: ” + value), () -> System.out.println(“Not found”) );
In a type declaration the ! is similar to the ?. Both are an optional, but the ! is an “implicitly unwrapped” optional, meaning that you do not have to unwrap it to access the value (but it can still be nil). This is basically the behavior we already had in objective-c. A value can … Read more
Take these two scenarios: Optional<Foo> opt = … Foo x = opt.orElse( new Foo() ); Foo y = opt.orElseGet( Foo::new ); If opt doesn’t contain a value, the two are indeed equivalent. But if opt does contain a value, how many Foo objects will be created? P.s.: of course in this example the difference probably … Read more
if let and guard let serve similar, but distinct purposes. The “else” case of guard must exit the current scope. Generally that means it must call return or abort the program. guard is used to provide early return without requiring nesting of the rest of the function. if let nests its scope, and does not … Read more
It is almost always unnecessary to check if an optional is not nil. Pretty much the only time you need to do this is if its nil-ness is the only thing you want to know about – you don’t care what’s in the value, just that it’s not nil. Under most other circumstances, there is … Read more
Oh, those coding styles are to be taken with a bit of salt. (+) Passing an Optional result to another method, without any semantic analysis; leaving that to the method, is quite alright. (-) Using Optional parameters causing conditional logic inside the methods is literally contra-productive. (-) Needing to pack an argument in an Optional, … Read more
Before I can describe the use cases for Implicitly Unwrapped Optionals, you should already understand what Optionals and Implicitly Unwrapped Optionals are in Swift. If you do not, I recommend you first read my article on optionals When To Use An Implicitly Unwrapped Optional There are two main reasons that one would create an Implicitly … Read more
What does it mean to “unwrap the instance”? Why is it necessary? As far as I can work out (this is very new to me, too)… The term “wrapped” implies we should think of an Optional variable as a present, wrapped in shiny paper, which might (sadly!) be empty. When “wrapped”, the value of an … Read more
Of course, people will do what they want. But we did have a clear intention when adding this feature, and it was not to be a general purpose Maybe type, as much as many people would have liked us to do so. Our intention was to provide a limited mechanism for library method return types … Read more