MIGRATION2-3.md

Migrating from 2.0.0 to 3.x.x

ViewEvent

Handling of a ViewEvent has been greatly simplified. You now can just call handle() on an event and pass it a lambda expression that will only be called if the event has not been handled already. Internally the event is marked as "handled" before the expression is invoked.

Old and no longer supported method:

viewModel.state.observe(this, Observer {
    ...
    if (!it.event.handled) {
        when (it.event) {
            is CatViewEvent.Meow -> {
               it.event.handled = true
               // show Meow! dialog
            }
            is CatViewEvent.Sleep -> {
               it.event.handled = true
               // finish Activity
            }
        }
    }
})

New and simplified way:

viewModel.state.observe(this, Observer {
    ...
    when (it.event) {
       is CatViewEvent.Meow -> it.event.handle { // show Meow! dialog }
       is CatViewEvent.Sleep -> it.event.handle { // finish Activity }
    }
})

Result

Result has been split into Result and LiveResult. Result now no longer provides a Pending variant, since commands with continous status updates are rare and the combined API polluted simple commands.

Commands with intermediate status updates are still supported with the new LiveResult class which also allows different types for pending and success data.

Result.Error no longer has a data property. This is more in line with the semantics of an "error" and you don't have to set a default value as a fallback anymore. This was especially cumbersome when returning results with Data Classes where you had to provide some kind of "empty" class in errors.

Status

Result and Resource no longer provide a status property, since it was redundant to the actual type. Use the extension functions like fold() instead, if you previously relied on status for processing results. The Status enum has therefore also been removed.

Resource

The "failed" variant of Resource has gone through some naming changes to stay consistent with the new LiveResult type:

2.0.0	3.x.x
Resource.Error	Resource.Failure
errorValue()	failureValue()
isError {}	isFailure {}