Struct LazyItems 

pub struct LazyItems { /* private fields */ }

A run of lazy items: how many, and optionally how they are identified and reused.

A count converts into this on its own, so the ordinary list reads as scope.items(20, |index| ...) — the shape Compose gets from default arguments, which Rust does not have. A list whose contents move between compositions names a key so item state follows the item rather than the slot it happened to occupy:

scope.items(LazyItems::new(rows.len()).key(|index| rows[index].id), |index| {
    Row(&rows[index]);
});

Implementations

impl LazyItems

pub fn new(count: usize) -> LazyItems

A run of count items with no key and no reuse class.

pub fn key(self, key: impl Fn(usize) -> u64 + 'static) -> LazyItems

Gives each item a stable identity, so state, animations and scroll position follow the item when the list is reordered or edited.

pub fn content_type( self, content_type: impl Fn(usize) -> u64 + 'static, ) -> LazyItems

Groups items into reuse classes, so a scrolling list recycles a row into another row of the same shape rather than rebuilding it.

pub fn count(&self) -> usize

How many items this run declares.

pub fn key_fn(&self) -> Option<Rc<dyn Fn(usize) -> u64>>

The identity function, if the caller named one.

pub fn content_type_fn(&self) -> Option<Rc<dyn Fn(usize) -> u64>>

The reuse-class function, if the caller named one.

Trait Implementations

impl Clone for LazyItems

fn clone(&self) -> LazyItems

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Default for LazyItems

fn default() -> LazyItems

Returns the “default value” for a type.

impl From<usize> for LazyItems

fn from(count: usize) -> LazyItems

Converts to this type from the input type.