`while (value.links.next != null) {` any chance to smartcast value.links.next to non-null inside the...

# announcements

[df]

while (value.links.next != null) { any chance to smartcast value.links.next to non-null inside the loop? Basically looking for a counterpart to nullable?.let { it is not null }

[Rajkumar Singh]

value.links.forEach { if (it.next != null) {} else {} }.... something like this might work

[df]

value.links is not a list 🙂

[df]

while (value.links.next != null) {
    doSomething(value); 
    value = getNextPage(value.links.next) 
}

that's more or less the code I have at hand

[Rajkumar Singh]

what about value & value.links ? are they not null values?

[Rajkumar Singh]

only next could be null?

[Vampire]

value is mutable, so nothing can be smart-casted as a different thread could modify it in the meantime.

[Nir]

@df maybe use generateSequence?

[Nir]

maybe something like:

for ((value, next) in generateSequence { if (value.links.next != null) value to next else null }) { ... }

[Nir]

might be more readable with forEach instead of a for loop

[nanodeath]

might be a rare good opportunity for tail recursion

[df]

maybe easier to help with the full code

[df]

https://gist.github.com/dfreudenberger/d70d315b0e78ded9341575a07bc59ae9

[df]

obv. it's working I just don't like the way it "looks" 😉

[Nir]

var firstRequest = true

    generateSequence("/api/rest/v1/products") {
        val response = httpClient.get<ResultPage<Product>> {
            url(it)
            header("Authorization", "Bearer ${token.accessToken}")
            if (firstRequest) {
                contentType(ContentType.Application.Json)
                parameter("search", objectMapper.writeValueAsString(search))
                params.forEach { k, v -> parameter(k, v) }
                firstRequest = false
            }
        }
        send(response)
        response.links.next?.href
    }.takeWhile { true }

[Nir]

ideally there should really be a function called takeAll instead

[gildor]

I prefer this way to handle it:

while (true) {
    val value = value.links.next ?: break
    doSomething(value)
}

It makes value immutable, smart cast works as expected, it very flexible

One may doesn't like while(true) estetically, but on practice I don't see big issue there, especially because it provides many benefits

Actual implementation may be different, depending on scope, but it just general idiom, use while(true) + elvis with break to make smart cast work