DEV Community

Discussion on: State transitions (i.e. Elm messages/React actions etc.): Past or imperative tense?

drbearhands profile image
DrBearhands

If you're talking about commands as in Cmd msg, I disagree. Commands are imperative by definition.
For messages caused by a Sub msg, that does make a degree of sense.
For messages pushed by the execution of some command, maybe. You could say (a) firstCmd |> Cmd.map doSecondCmd or (b) someCmd |> Cmd.map firstCmdDone. (a) communicates intent directly in the execution of the command, (b) does not communicate intent directly, but elsewhere the update function. Considering update is supposed to handle and react to messages (b) seems to be "correct" most often, but in cases where the handling of the message logic is shared by multiple commands, (a) might be a better fit.

Thread Thread
nimmo profile image
Nimmo Author • Edited on

I was thinking specifically with the example I posted initially to be honest:

StartGame, ChangedUrl, ChangeRoom

Now you can see what effects the user intentionally chose, and which one was a side-effect of something that they chose to do.

Thread Thread
nimmo profile image
Nimmo Author

Of course, the inverse of that is that the user can in fact change the URL for themselves, so I guess this hasn't actually helped anything at all. D'oh.

Thread Thread
drbearhands profile image
DrBearhands

It depends on what those messages are.

GameMsg ToggleInventory, will it, when passed to update, create a new Model that when passed to view will show an inventory? Then imperative makes sense.

If you'd use the name InventoryToggled to denote that the user has e.g. pressed the ToggleInventory button, I'd say you're naming things incorrectly because the inventory wasn't toggled, as the message has not been processed by update yet.

ChangedUrl on the other hand denotes something that definitely did happen. It is more similar to ToggleInventoryButtonPressed.

Thread Thread
nimmo profile image
Nimmo Author

Yeah, the more I think about it the more I think mixed tense (but intentionally so, rather than accidentally so) feels like the way forward here.

Appreciate your input, this has been a useful conversation.

Thread Thread
drbearhands profile image
DrBearhands

Glad it was of use to you