Kas saaksite selgitada Optional Publisher kontseptsiooni ja millistes olukordades seda kasutatakse?

Optional Publisher — is a concept in reactive programming where a Publisher can either publish a single value or nothing (i.e., complete without values). For example, in Swift Combine, this can be an Optional combined with a Publisher, which either emits a value or immediately completes.

An Optional Publisher is used when the result may be absent, but you still want to maintain a reactive style of data processing without errors or special values. It is useful for wrapping optional values into a data stream.

Example in Swift Combine:

let optionalValue: Int? = 42

let publisher = optionalValue.publisher

publisher.sink(receiveCompletion: { completion in
    print("Completed: \(completion)")
}, receiveValue: { value in
    print("Value: \(value)")
})

If optionalValue is nil, the Publisher will immediately complete without values.