For completion, we should offer an As method like the one in Go 1.13 errors (https://golang.org/pkg/errors/#As). We should try to make this more reliable than Go's version by preventing panics: "As will panic if target is not a non-nil pointer to either a type that implements error, or to any interface type." Seems like we could just return false in these cases instead.

I'm submitting a ...

[x] Feature request

Current behavior

Actually there is only a reactive way how to invoke an error message, either on submit or on blur and both of them depend on a user's action.

Expected behavior

There are cases in some more complex forms where the business logic dictates