Already the second time now in unit tests that it would be n kotlinlang #arrow

Already the second time (now in unit tests) that it would be nice to have something in the Kotlinx serialization optics library a way to get a lens to a

List<String>

on the `name`s here:

[{ "id":1, "name": "this"}, {"id":2, "name": "that"}]

Sam

03/29/2023, 1:43 PM

If only this was Groovy, you could just write

list.name

:trollface:

simon.vergauwen

03/29/2023, 1:44 PM

JsonPath.every.select("name")

works for this, no?

JsonPath.every.select("name").getOrNull(jsonElement)

dave08

03/29/2023, 1:45 PM

Nope, that gives a

List<JsonElement>

simon.vergauwen

03/29/2023, 1:45 PM

JsonPath.every.select("name").string.getOrNull(jsonElement)

Alejandro Serrano Mena

03/29/2023, 1:47 PM

you always need something like

string

to ensure that you’re targeting the right type of element

dave08

03/29/2023, 1:48 PM

👍🏼 It seems like that does it, but there's no

getOrNull

there, just

getAll

...?

This is all a bit confusing about Optics... I'm still not sure what returns what and when...

Alejandro Serrano Mena

03/29/2023, 1:49 PM

I think it should be

getAll

in this case, since you want to return a list of elements

dave08

03/29/2023, 1:50 PM

image.png

Alejandro Serrano Mena

03/29/2023, 1:50 PM

• `getAll`returns List<T>, available for Every, Optional, Prism, Lens •

getOrNone

returns Option<T>, available for Optional, Prism, Lens • `get`` returns T, available for Lens

PEvery<JsonElement, JsonElement, String, String

is equivalent to

Every<JsonElement, String>

dave08

03/29/2023, 1:52 PM

So I'm using Every here? Why do PTraversal and PSetter appear there and when would I use them?

For setting that list "in place"?

Alejandro Serrano Mena

03/29/2023, 1:57 PM

sorry, my bad, I meant to mention

Every

in the list above

the reason why you get the others is because optics form a hierarchy

a Every is a Traversal, which is both a Fold (which is the base interface containing

getAll

) and a Setter (which is the base interface containing

modify

)

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