Yes, Google people always have to do some big-brain stuff in their projects.
I’m sure the initial reasons for their state management were valid and their heart was pure, but god damn it’s a mess.
I’m sure the initial reasons for their state management were valid and their heart was pure, but god damn it’s a mess.
It mostly extends from the fact that the Flutter community in general is stuck on a perpetual loop talking about it because there is no “one true way blessed by Google wrapped up into a single package that is appropriate for all use cases”.
But in practice it’s exactly the same as any other OOP language or framework where you can pick from multiple paradigms depending on your use case.
Want to use a state machine? There are options for that. Same goes for Rx patterns, local state, redux patterns and more.
There are a lot of extremely complicated apps who don’t have any issue with it in reality and the drama is very much a community problem rather than a real issue.
The GUI components would be aware when their state changed and would update its own display. But now you can't do that anymore - either you redraw the whole screen or not at all.
You could receive/send data asynchronously if needed in a separate thread and update the main thread which managed the GUI etc. None of this required jumping through hoops like we are doing now.
Example: This is how data could be fetched asynchronously and the UI updated on termination of the call in Delphi:
procedure TMainForm.ButtonClick(Sender: TObject);
begin
RESTRequest.ExecuteAsync(
procedure
begin
Memo.Lines.Add(RESTResponse.Content);
end,
True, True,
procedure(Error: TObject)
begin
Memo.Lines.Add(Exception(Error).Message);
end;
Note: even with all of the Pascal ceremony of begin/end etc, this code is more succinct and far cleaner and much easier to debug than the state/stateless nonsense that is spread out all over a Flutter codebase.
And yes, I do remember that Visual C++ had a bit of a convoluted state management logic for MFC.
I wrote and maintained a lot of large GUI applications in that style during that time, as well as building a couple of GUI frameworks that operated that way.
It's fine for a while and as long as the UI is fairly static and there's mostly a 1:1 mapping between pieces of data and UI that shows it. But it scales horribly once you find yourself in a situation where you have lots of computed model data, or model data that is shown in many places in the UI, or a highly flexible UI that changes a lot. You end up in a sprawling mess of event handlers, orphaned bits of UI that aren't on screen but are still inadvertently listening to events, zombie UI that forgot to register an event handler and isn't updating, computer model state that for now good reason lives inside one random button, and then other UI code that is pulling that state from that button and breaks if the button isn't on screen, etc.
The reactive style / immediate mode style where you essentially redraw the entire UI based on the current model state is so much simpler and cleaner.
Yes, state management can still be weird, but that's because mutable state is hard. There's no silver bullet.
How often do you show more than one screen open at a time in a mobile app?
How often would you then need to display the same data field in multiple screens?
I think the state management in mobile apps is extremely over engineered for a use case that rarely ever happens.
First off, you have to decide where the selection itself is stored. Is whether or not an item is selected "model" state? Or "view model"? If the latter, is there a well defined place where that kind of data is stored or does it literally just list in the list UI element itself? If so, how do all of the other UI elements that need that state get it? Are they directly coupled to the list box?
If a user selects "undo" does that change the selection? Is selecting or unselecting an item and undoable operation or not?
If the back-end server sends an update that some item is no longer available, does the UI handle that appropriately?
When the budget number changes, where does the validation logic to ensure the user chooses a reasonable number live?
This is just a very simple example, but stuff like this comes up all the time and gets gnarly real fast.
Also, MVC as a concept has existed for decades. GUI controls have always had a concept of a "onChange" events and when it came to the code which fetches changes from the server, there were multiple ways of handling that - from using polling, to using message queues to using db triggers, from using plain socket calls etc.
And also very sophisticated applications with literally 100s of screens - example: plane/hotel ticketing apps, stock trading applications, ERP/MRP software etc, have all existed for decades.
Yes, and many of those applications are being migrated from an event-based architecture to a reactive one because their authors find them easier to maintain.
The existence of the Stateless vs Stateful widgets, the "class YourState extends State<>" classes, you can't put a stateful widget inside a stateless widget and a range of many other things that aren't at the top of my mind right now.
Of course that are valid reasons of all of this, of course there are "other better ways", but when a large part of your user base wrestles with this for years, it really doesn't matter how smart and correct you are because it is in fact a problem.
def main(page: ft.Page): page.title = "Flet counter example" page.vertical_alignment = ft.MainAxisAlignment.CENTER
txt_number = ft.TextField(value="0", text_align=ft.TextAlign.RIGHT, width=100)
def minus_click(e):
txt_number.value = str(int(txt_number.value) - 1)
page.update()
def plus_click(e):
txt_number.value = str(int(txt_number.value) + 1)
page.update()
page.add(
ft.Row(
[
ft.IconButton(ft.icons.REMOVE, on_click=minus_click),
txt_number,
ft.IconButton(ft.icons.ADD, on_click=plus_click),
],
alignment=ft.MainAxisAlignment.CENTER,
)
)If you happen to like that approach more that’s cool keep using it but it’s not the done thing in any mainstream modern UI framework that I’m aware of for a reason.