Java 8’s Optional was mainly intended for return values from methods, and not for properties of Java classes, as described in Optional in Java SE 8: 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 … Read more
There’s no null in Rust (and no Null Pointer Exception, Rust is designed for safety). You must either 1) use an option (i.e. a field of type Option<TcpStream>) 2) or better: return a result when building the struct Here, the best option would probably be to connect from inside a function returning a Result<FistClient>, so … Read more
The arguments for a method are always evaluated before the method is called. You want orElseGet which takes a Supplier that will only be invoked if the Optional is not present: private Field getField(Class<?> clazz, String p) { return Arrays.stream(clazz.getDeclaredFields()) .filter(f -> p.equals(f.getName())) .findFirst() .orElseGet(() -> getField(clazz.getSuperclass(), p)); }
You (Matt) probably know at least some of this already, but here are some facts for other readers: Swift infers types on one whole statement at a time, but not across statements. Swift allows type inference to automatically promote an object of type T to type Optional<T>, if necessary to make the statement type-check. Swift … Read more
I believe what is happening is that the literal 1 is being implicitly typecast to the Int? type by the comparison to nil. For those who aren’t used to Swift, I’ll explain a little further. Swift has a concept called “optionals”, which can either have a value or be nil. (For anyone familiar with Haskell, … Read more
A logical solution would be to use *string as mentioned by Ainar-G. This other answer details the possibilities of obtaining a pointer to a value (int64 but the same works for string too). A wrapper is another solution. Using just string An optional string means a string plus 1 specific value (or state) saying “not … Read more
This might work: final scala.Option<String> x = scala.Option.apply(null); def apply [A] (x: A): Option[A] An Option factory which creates Some(x) if the argument is not null, and None if it is null.
With Java 9 or higher, ifPresentOrElse is most likely what you want: Optional<> opt = dao.find(); opt.ifPresentOrElse(obj -> obj.setAvailable(true), () -> logger.error(“…”)); Currying using vavr or alike might get even neater code, but I haven’t tried yet.
Replace get() with orElse(null).
In Xcode Beta 5, they no longer let you do: var xyz : NSString? if xyz { // Do something using `xyz`. } This produces an error: does not conform to protocol ‘BooleanType.Protocol’ You have to use one of these forms: if xyz != nil { // Do something using `xyz`. } if let xy … Read more