Struct relm4::factory::DynamicIndex

pub struct DynamicIndex { /* private fields */ }

A dynamic index that updates automatically when items are shifted inside a factory container.

For example a FactoryVecDeque has an insert method that allows users to insert data at arbitrary positions. If we insert at the front all following widgets will be moved by one which would invalidate their indices. To allow widgets in a factory container to send messages with valid indices this type ensures that the indices is always up to date.

Never send an index as usize but always as DynamicIndex to the update function because messages can be queued up and stale by the time they are handled.

DynamicIndex is a smart pointer so cloning will work similar to std::rc::Rc and will create a pointer to the same data.

In short: only call current_index from the update function where you actually need the index as usize.

Implementations

impl DynamicIndex

pub fn current_index(&self) -> usize

Get the current index number.

This value is updated by the factory container and might change after each update function.

Examples found in repository

relm4/examples/to_do.rs (line 131)

    fn update(&mut self, msg: AppMsg, _sender: ComponentSender<Self>) {
        match msg {
            AppMsg::DeleteEntry(index) => {
                self.tasks.guard().remove(index.current_index());
            }
            AppMsg::AddEntry(name) => {
                self.tasks.guard().push_back(name);
            }
        }
    }

relm4/examples/grid_factory.rs (line 220)

    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
        let mut counters_guard = self.counters.guard();

        match msg {
            AppMsg::AddCounter => {
                counters_guard.push_back(self.created_widgets);
                self.created_widgets = self.created_widgets.wrapping_add(1);
            }
            AppMsg::RemoveCounter => {
                counters_guard.pop_back();
            }
            AppMsg::SendFront(index) => {
                counters_guard.move_front(index.current_index());
            }
            AppMsg::MoveDown(index) => {
                let index = index.current_index();
                let new_index = index + 1;
                // Already at the end?
                if new_index < counters_guard.len() {
                    counters_guard.move_to(index, new_index);
                }
            }
            AppMsg::MoveUp(index) => {
                let index = index.current_index();
                // Already at the start?
                if index != 0 {
                    counters_guard.move_to(index, index - 1);
                }
            }
        }
    }

relm4/examples/entry.rs (line 127)

    fn update(&mut self, message: Self::Input, _sender: ComponentSender<Self>) {
        match message {
            AppMsg::AddCounters => {
                let text = self.entry.text();
                if let Ok(v) = text.parse::<i32>() {
                    let mut guard = self.counters.guard();
                    if v.is_positive() {
                        // add as many counters as user entered
                        for _ in 0..v {
                            guard.push_back(self.created_counters);
                            self.created_counters += 1;
                        }
                    } else if v.is_negative() {
                        // remove counters
                        for _ in v..0 {
                            guard.pop_front();
                        }
                    }

                    // clearing the entry value clears the entry widget
                    self.entry.set_text("");
                }
            }
            AppMsg::Clicked(index) => {
                if let Some(counter) = self.counters.guard().get_mut(index.current_index()) {
                    counter.value = counter.value.wrapping_sub(1);
                }
            }
        }
    }

relm4/examples/factory.rs (line 197)

    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
        let mut counters_guard = self.counters.guard();
        match msg {
            AppMsg::AddCounter => {
                counters_guard.push_back(self.created_widgets);
                self.created_widgets = self.created_widgets.wrapping_add(1);
            }
            AppMsg::RemoveCounter => {
                counters_guard.pop_back();
            }
            AppMsg::SendFront(index) => {
                counters_guard.move_front(index.current_index());
            }
            AppMsg::MoveDown(index) => {
                let index = index.current_index();
                let new_index = index + 1;
                // Already at the end?
                if new_index < counters_guard.len() {
                    counters_guard.move_to(index, new_index);
                }
            }
            AppMsg::MoveUp(index) => {
                let index = index.current_index();
                // Already at the start?
                if index != 0 {
                    counters_guard.move_to(index, index - 1);
                }
            }
            AppMsg::Remove(index) => {
                counters_guard.remove(index.current_index());
            }
        }
    }

relm4/examples/factory_async.rs (line 225)

    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
        let mut counters_guard = self.counters.guard();
        match msg {
            AppMsg::AddCounter => {
                counters_guard.push_back(self.created_widgets);
                self.created_widgets = self.created_widgets.wrapping_add(1);
            }
            AppMsg::RemoveCounter => {
                counters_guard.pop_back();
            }
            AppMsg::SendFront(index) => {
                counters_guard.move_front(index.current_index());
            }
            AppMsg::MoveDown(index) => {
                let index = index.current_index();
                let new_index = index + 1;
                // Already at the end?
                if new_index < counters_guard.len() {
                    counters_guard.move_to(index, new_index);
                }
            }
            AppMsg::MoveUp(index) => {
                let index = index.current_index();
                // Already at the start?
                if index != 0 {
                    counters_guard.move_to(index, index - 1);
                }
            }
            AppMsg::Remove(index) => {
                counters_guard.remove(index.current_index());
            }
        }
    }

Trait Implementations

impl Clone for DynamicIndex

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DynamicIndex

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq<DynamicIndex> for DynamicIndex

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for DynamicIndex