Recipe to set Select values dynamically?

[thomastiotto]

I'm trying to implement a Select component whose values are not hardcoded but loaded dynamically.
To this end I have a State.get_values() function that generates these values and writes them to State._values. As I couldn't get the Select to work as I would have expected (i.e. rx.select(State._values)) I tried to define a read_values() function that returns the State._values variable.

My frontend code is as follows:

def read_values() -> list[str]:
    return State._values

@rx.page(on_load=State.get_values)
def symbols() -> rx.Component:
    return rx.select(State.get_values)

while my backend is like this:

class State(rx.State):
    _values : list[str] = []

    def get_values(self):
        self._values = ["a","b"]

No matter what I try I can't get the Select to show the values that I have loaded into the State. By debugging I see that read_values() is called before the page loads and that State.get_values is called after that, but then I can't get read_values() to be called again, so it makes sense that the component is displaying [].

Am I approaching this the correct way or is there another way or dealing with this kind of problem?

EDIT:
I finally managed to get it to work by changing my code this way, even though I'm not sure what @rx.cached_var is doing:
frontend:

@rx.page(on_load=State.load_values)
def symbols() -> rx.Component:
    return rx.select(read_values())

while my backend is like this:

class State(rx.State):
    _values : list[str] = []

    @rx.cached_var
    def get_values(self) -> list[str]:
        values = self._values
        return values

    def load_values(self):
        self._values = ["a","b"]

[picklelo]

@thomastiotto take a look at our select docs to see how to bind your select to state.

Your code can be simplified to be

class State(rx.State):
    values : list[str] = []

    def load_values(self):
        self.values = ["a","b"]

and

rx.page(on_load=State.load_values)
def symbols() -> rx.Component:
    return rx.select(State.values)