Struct relm4::factory::collections::DynamicIndex

pub struct DynamicIndex { /* private fields */ }

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

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 to still 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 or even better as WeakDynamicIndex 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 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.

Panics

Sending a DynamicIndex to a different thread and accessing it will panic.

Implementations

impl DynamicIndex

pub fn current_index(&self) -> usize

Get the current index number.

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

Examples found in repository

relm4-examples/examples/factory_advanced_manual.rs (line 44)

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    fn update(&mut self, msg: AppMsg, _components: &(), _sender: Sender<AppMsg>) -> bool {
        match msg {
            AppMsg::AddFirst => {
                self.counters.push_front(Counter {
                    value: self.received_messages,
                });
            }
            AppMsg::RemoveLast => {
                self.counters.pop_back();
            }
            AppMsg::CountAt(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    if let Some(counter) = self.counters.get_mut(index.current_index()) {
                        counter.value = counter.value.wrapping_sub(1);
                    }
                }
            }
            AppMsg::RemoveAt(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.remove(index.current_index());
                }
            }
            AppMsg::InsertBefore(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.insert(
                        index.current_index(),
                        Counter {
                            value: self.received_messages,
                        },
                    );
                }
            }
            AppMsg::InsertAfter(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.insert(
                        index.current_index() + 1,
                        Counter {
                            value: self.received_messages,
                        },
                    );
                }
            }
        }
        self.received_messages += 1;
        true
    }

relm4-examples/examples/factory_advanced.rs (line 44)

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    fn update(&mut self, msg: AppMsg, _components: &(), _sender: Sender<AppMsg>) -> bool {
        match msg {
            AppMsg::AddFirst => {
                self.counters.push_front(Counter {
                    value: self.received_messages,
                });
            }
            AppMsg::RemoveLast => {
                self.counters.pop_back();
            }
            AppMsg::CountAt(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    if let Some(counter) = self.counters.get_mut(index.current_index()) {
                        counter.value = counter.value.wrapping_sub(1);
                    }
                }
            }
            AppMsg::RemoveAt(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.remove(index.current_index());
                }
            }
            AppMsg::InsertBefore(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.insert(
                        index.current_index(),
                        Counter {
                            value: self.received_messages,
                        },
                    );
                }
            }
            AppMsg::InsertAfter(weak_index) => {
                if let Some(index) = weak_index.upgrade() {
                    self.counters.insert(
                        index.current_index() + 1,
                        Counter {
                            value: self.received_messages,
                        },
                    );
                }
            }
        }
        self.received_messages += 1;
        true
    }

pub fn downgrade(&self) -> WeakDynamicIndex

Creates a WeakDynamicIndex for sending in messages.

Examples found in repository

relm4-examples/examples/factory_advanced_manual.rs (line 115)

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    fn init_view(&self, index: &DynamicIndex, sender: Sender<AppMsg>) -> FactoryWidgets {
        let hbox = gtk::Box::builder()
            .orientation(gtk::Orientation::Horizontal)
            .spacing(5)
            .build();

        let counter_button = gtk::Button::with_label(&self.value.to_string());
        let index: DynamicIndex = index.clone();

        let remove_button = gtk::Button::with_label("Remove");
        let ins_above_button = gtk::Button::with_label("Add above");
        let ins_below_button = gtk::Button::with_label("Add below");

        hbox.append(&counter_button);
        hbox.append(&remove_button);
        hbox.append(&ins_above_button);
        hbox.append(&ins_below_button);

        {
            let sender = sender.clone();
            let index = index.clone();
            counter_button.connect_clicked(move |_| {
                send!(sender, AppMsg::CountAt(index.downgrade()));
            });
        }

        {
            let sender = sender.clone();
            let index = index.clone();
            remove_button.connect_clicked(move |_| {
                send!(sender, AppMsg::RemoveAt(index.downgrade()));
            });
        }

        {
            let sender = sender.clone();
            let index = index.clone();
            ins_above_button.connect_clicked(move |_| {
                send!(sender, AppMsg::InsertBefore(index.downgrade()));
            });
        }

        ins_below_button.connect_clicked(move |_| {
            send!(sender, AppMsg::InsertAfter(index.downgrade()));
        });

        FactoryWidgets {
            hbox,
            counter_button,
        }
    }

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: &DynamicIndex) -> bool

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

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

This method tests for !=.

impl Eq for DynamicIndex

impl StructuralEq for DynamicIndex

impl StructuralPartialEq for DynamicIndex