PickList requires Copy trait, severely limiting its use

[olson-dan]

I have something like this:

#[derive(Debug, Clone, PartialEq, Eq)]
struct Item {
  id: u32,
  description: String,
}

impl std::fmt::Display for Item {
 // ...
}

struct State {
  items: Vec<Item>,
  selected_item: Option<Item>,
  dropdown: pick_list::State<Item>
}

// ...

fn view(&mut self) -> Element<Message> {
  // ...
  let dropdown = PickList::new(&mut self.dropdown,
    &self.items,
    self.selected_item,
    Message::ItemSelected);
  // ...
}

This does not work because the third parameter to PickList::new() takes an Option<T> and requires Copy to be implemented. This prevents any type that implements String from being used with PickList, which is highly limiting.

[twitchyliquid64]

Have a look at #467 - basically just have the T in PickList be an index (ie: fixed-size newtype) into state at a higher scope, and implement impl std::fmt::Display to resolve that string.

[olson-dan]

Have a look at #467 - basically just have the T in PickList be an index (ie: fixed-size newtype) into state at a higher scope, and implement impl std::fmt::Display to resolve that string.

Thanks for the suggestion. Pardon me if I'm not following along, but how would one pass state into a Display implementation without storing it in the struct or using a global?

[hecrj]

We may be able to accept a reference as the third argument. I'll look into it!

For the time being, you should be able to circumvent the issue with an explicit clone: self.selected_item.clone().

[olson-dan]

For the time being, you should be able to circumvent the issue with an explicit clone: self.selected_item.clone().

Thanks, it was silly of me to not try that!