[2.4.6-Scala] JsResult; match or fold ?

[Gervais Blaise]

Hi there,

While reading the documentation about Json. There is one example who use `JsResult.fold` to process the `errors` or json object, in the next page, there is another example who use pattern matching against `JsSuccess` and `JsError`. This is, no doubt a trivial or troll questions but. Is it a recommandation or best practices to use `fold` or pattern matching ?

Thanks

[Daniel Manchester]

Hi,

I haven't worked with JsResult before, but it looks like an either-or type (an instance is either a JsSuccess or a JsError), somewhat similar to a Scala Option (either a Some or a None).

Option offers a fold() method, too, which has been criticized for a lack of readability. See, for example, "Option.fold() considered unreadable". I imagine those criticisms would also apply to JsResult's fold().

In fact, the authors of Play's "JSON basics" documentation (what I believe you were looking at) pretty much admit there's a readability issue: there's no programmatic reason to specify the argument names as they do...

    fold(invalid = ..., valid = ...)

...so I presume they did it to reduce confusion.

So yeah, I think pattern matching would be better. Or, maybe you could do some kind of JsResult.map(...).getOrElse(...) construction, as the above blog post does with Option?

Dan