Was also wondering if there could be a `foo.validate { }` using optics to return an `Either<Nel&l...

# arrow

[dave08]

Was also wondering if there could be a foo.validate { } using optics to return an Either<Nel<ValidationError>, Foo> for validating data class hierarchies after they were deserialized...?

[dave08]

It could be used when ensure and zipOrAccumulate can't be used, because object instantiation isn't in the app code's control...

[Alejandro Serrano Mena]

how would you envision it working?

[dave08]

val foo = Foo(...)

val result: Either<ValidationError, Foo> = foo.validate {
   Foo.baz eq 20
   Foo.bar.bara.barb eq "something"
 }

[dave08]

Each line that doesn't pass could be accumulated in the Left.

[dave08]

And if they all pass, Right is returned with Foo

[dave08]

Does this make any sense @Alejandro Serrano Mena? It's you that had the great idea to add copy { }... I just thought to use the same pattern for validation...!

[Alejandro Serrano Mena]

the problem here is that usually to call validate you don’t have a working value, you want to construct it when validation is successful

[Alejandro Serrano Mena]

this may work with a prism, but would need a bit more work

[dave08]

you don’t have a working value

I'm not sure I understand...? I fixed up my example above, we already HAVE an instance of foo... we're just returning it if it validates.

[dave08]

Just like you run copy { } on an instance.

[dave08]

this may work with a prism

I really don't understand what a prism IS (or any other of these constructs except for setter and getter...)

[dave08]

And there's no tutorials out there that explain it apart from those docs being worked on...

[dave08]

I was looking at the Copy implementation, and was thinking maybe something like this might be easier/more flexible? Is this possible @Alejandro Serrano Mena?

val foo = Foo(...)

val result: Either<ValidationError, Foo> = foo.validate {
   Foo.baz ensureThat { it == 20 }
   Foo.bar.bara.barb ensureThat { it.startsWith("something") }
 }