Converting enum to string

[dorukotiv]

Feature Description

Currently, an enum that is defined in slint can not be given to the Text component as an input, a callback needs to be implemented in Rust to do the conversion.

Ideally, I would directly use the enum text as an input to the text.

Example:

enum Direction {
Right,
Left
}

Text {
text : Direction.Right;
}

that would be seen as "Right" on the screen.

Product Impact

We are a railway company building Remote Supervision Control Desktop application for a locomotive.

It would reduce the code and time.

[tronical]

I don't feel very comfortable with this. Other programming languages don't do this typically out of the box with enums and use reflection instead. And to make matters worse: this doesn't play well with translations.

Perhaps we need a way to more easily create mappings? Like a match on an enum that errors when not all variants are covered.

[ogoffart]

(in case you didn't know, it is converting to string for debugging purpose using the debug(...) function to print value in the console)

You can use @rust-attr to derive from one of the crate that provide enum-to-string conversion in rust for the exported rust enum.

But I agree with @tronical that this is not necessarily a good idea to have that in Slint itself.

[tronical]

I suggest we don't implement this. But I'd like the ability for user to write something like this:

function direction-string(dir: Direction): string {
    match dir {
        Direction.Left => "left",
        // compiler errors out, because `Right` isn't handled here
    }
}

[ogoffart]

We already have a tracking issue for a match or switch: #1307

In the mean time, it can be done with something like:

function direction-string(dir: Direction): string {
    return dir == Direction.Left ? "left"
         : dir == Direction.Right ? "right"
         : ""; // unfortunately no errors/warnings at this point
    }
}

or in rust with a callback that does to-string based on @rust-attr(derive(strum_macros::Display))