Confusing over Vec and Dyn (NewB q)

[RemCode]

Hello World,

i have some structs like Control .Control>Edit> enz
how do I put those in a vec!
Here is sample code that better explains what i am trying to do

pub trait ControlMarker {} 
#[derive(Default)]
pub struct Control<D: ControlMarker> {
    name: String,
    _isFocused: bool,
    _isVisible: bool,
    _isEnabled: bool,
    _Flags: u8,
    _control: D,
}
impl<T: ControlMarker> Control<T> {
    pub fn SetIsFocused(&mut self, new_focus: bool) {
        self._isFocused = new_focus
    }
    pub fn SetIsVisible(&mut self, new_visible: bool) {
        self._isVisible = new_visible
    }
    pub fn SetIsEnabled(&mut self, new_enabled: bool) {
        self._isEnabled = new_enabled
    }
    pub fn IsFocused(&self) -> bool {
        self._isFocused
    }
    pub fn IsVisible(&self) -> bool {
        self._isVisible
    }
    pub fn IsEnabled(&self) -> bool {
        self._isEnabled
    }
}
////////Toggle///////
#[derive(Default)]
pub struct Toggle {toggle: bool,}
impl ControlMarker for Toggle {}
impl Control<Toggle> {
    pub fn Flip(&mut self) {
        self._control.toggle = !(self._control.toggle)
    }
}
////////Editable///////
#[derive(Default)]
struct Editable {buffer: String,}
impl ControlMarker for Editable {}
impl Control<Editable> {
    pub fn StartEdit(&self) -> () { /* Strat here */
    }
}

impl ControlMarker for Box<(dyn ControlMarker + 'static)> {} // o o bad sign.....

struct Host {
    widgets: Vec<Control<Box<dyn ControlMarker>>>, // here starts the confusion....
}
impl Host {
    pub fn EnableAll(&mut self) {
        for w in &mut self.widgets {
            w.SetIsEnabled(true)
        }
    }
}

pub fn main() {
    let mut ToggleButton = Control::<Toggle>::default();
    let mut Entry = Control::<Editable>::default();

    Entry.StartEdit();
    ToggleButton.Flip();
    ToggleButton.SetIsEnabled(false);
    Entry.SetIsVisible(true);

    let cnt = Host {widgets: vec![(ToggleButton), (Entry)],}; // ofcourse this doent work :(
    cnt.EnableAll()
}

or platgound permalink

Regards,

Remco

[steffahn]

You’re having values of type Control<Toggle> and Control<Editable> and trying to put them into a Vec<Control<Box<dyn ControlMarker>>>. I’m not quite sure what the requirements in your code here are why you’re even needing trait objects. The code presented doesn’t have any methods in ControlMarker, so the use case for trait objects doesn’t entirely become clear.

If you want trait objects, there’s a few approaches to make your code example compile.

• You could offer a method on Control<T> that converts it into a Control<Box<dyn ControlMarker>>.
• You turn D into a ?Sized argument of Control<D> and use Box<Control<dyn ControlMarker>>.
• You could make Control<T> itself implement another trait (e.g. “ControlTrait”) and use Box<dyn ControlTrait>.

[RemCode]

Tnx! Steffahn ,

The requirements are that i get a Vec with items like:
Control[entry], Control[button], Control[List] enz.
I thought because of the 'T' i should use Dyn to store them in a Vec.
Am I wrong about that?

Nevertheless your solutions work.

Tnx again and regards,

Remco

[steffahn]

@RemCode

The requirements

Right, maybe that wasn’t clear: my main point was that as long as ControlMarker doesn’t have any methods, you’re basically storing some inaccessible garbage data in your Box<dyn ControlMarker> (well, at least unless they’re supposed to do important stuff when dropped). Thus assuming that your code presented may be a simplification of your actual setting, I was anticipating that there are more things to the ControlMarker trait or more ways in which the Vec<… Control … ControlMarker …> is used. And then, some of the proposed solutions might become infeasible once the simplifications are no longer in place. Or if there isn’t much more to the situation than what you presented, you might as-well swap out the ControlMarker types with some fixed dummy type before putting them into the Vec, so you don’t need trait objects at all.

[RemCode]

Learned some new things today

Remco