if let Some(origin) = resp.get(“origin”) { // use origin } If you can guarantee that it’s impossible for the value to be None, then you can use: let origin = resp.get(“origin”).unwrap(); Or: let origin = resp.get(“origin”).expect(“This shouldn’t be possible!”); And, since your function returns a Result: let origin = resp.get(“origin”).ok_or(“This shouldn’t be possible!”)?; Or with … Read more
It won’t compile because the function expecting a reference but you passed nil. The problem have nothing to do with optional. By declaring parameter with inout means that you will assign some value to it inside the function body. How can it assign value to nil? You need to call it like var a : … Read more
You can’t compare an arbitrary value to nil (EDIT: but see Sulthan’s comment below; it may be that we should be able to compare arbitrary values to nil; the rest of this paragraph may be true today, but only due to a compiler bug). While Optional has some bits of syntactic sugar applied to it, … Read more
Optional<User>.ifPresent() takes a Consumer<? super User> as argument. You’re passing it an expression whose type is void. So that doesn’t compile. A Consumer is intended to be implemented as a lambda expression: Optional<User> user = … user.ifPresent(theUser -> doSomethingWithUser(theUser)); Or even simpler, using a method reference: Optional<User> user = … user.ifPresent(this::doSomethingWithUser); This is basically the … Read more
The practical difference is this: var optionalString = dict[“SomeKey”] as? String optionalString will be a variable of type String?. If the underlying type is something other than a String this will harmlessly just assign nil to the optional. var optionalString = dict[“SomeKey”] as! String? This says, I know this thing is a String?. This too … Read more
Yes it’s correct An optional variable doesn’t need to be manually initialized. If you read it before having populated it does contain nil. From Apple docs If you define an optional variable without providing a default value, the variable is automatically set to nil for you […] On the other hand the compiler does force … Read more
In Java, an Optional value is a fusion of a bit that indicates presence or absence, with a value of an arbitrary reference type T or a primitive int, long, or double. Fusing these is especially useful when returning a value from a method, as methods have only a single return value. It’s often necessary … Read more
I’ll take another swing at this. Is this a valid usage? Yes, in the narrow sense that it compiles and produces the results that you’re expecting. Is this intended usage? No. Now, sometimes things find usefulness beyond what they were originally for, and if this works out, great. But for Optional, we have found that … Read more
Alternatively you can pattern match: case maybeValue of Just value -> … Nothing -> …
Actually what you are searching is: Optional.map. Your code would then look like: object.map(o -> “result” /* or your function */) .orElseThrow(MyCustomException::new); I would rather omit passing the Optional if you can. In the end you gain nothing using an Optional here. A slightly other variant: public String getString(Object yourObject) { if (Objects.isNull(yourObject)) { // … Read more