Trait slint::Model

pub trait Model {
    type Data;

    fn row_count(&self) -> usize;
    fn row_data(&self, row: usize) -> Option<Self::Data>;
    fn model_tracker(&self) -> &dyn ModelTracker;

    fn set_row_data(&self, _row: usize, _data: Self::Data) { ... }
    fn iter(&self) -> ModelIterator<'_, Self::Data> 
        Self: Sized
, { ... } fn as_any(&self) -> &(dyn Any + 'static) { ... } }
Expand description

A Model is providing Data for the Repeater or ListView elements of the .slint language

If the model can be changed, the type implementing the Model trait should holds a ModelNotify, and is responsible to call functions on it to let the UI know that something has changed.


As an example, let’s see the implementation of VecModel.

pub struct VecModel<T> {
    // the backing data, stored in a `RefCell` as this model can be modified
    array: std::cell::RefCell<Vec<T>>,
    // the ModelNotify will allow to notify the UI that the model changes
    notify: ModelNotify,

impl<T: Clone + 'static> Model for VecModel<T> {
    type Data = T;

    fn row_count(&self) -> usize {

    fn row_data(&self, row: usize) -> Option<Self::Data> {

    fn set_row_data(&self, row: usize, data: Self::Data) {
        self.array.borrow_mut()[row] = data;
        // don't forget to call row_changed

    fn model_tracker(&self) -> &dyn ModelTracker {

    fn as_any(&self) -> &dyn core::any::Any {
        // a typical implementation just return `self`

// when modifying the model, we call the corresponding function in
// the ModelNotify
impl<T> VecModel<T> {
    /// Add a row at the end of the model
    pub fn push(&self, value: T) {
        self.notify.row_added(self.array.borrow().len() - 1, 1)

    /// Remove the row at the given index from the model
    pub fn remove(&self, index: usize) {
        self.notify.row_removed(index, 1)

Required Associated Types§

The model data: A model is a set of row and each row has this data

Required Methods§

The amount of row in the model

Returns the data for a particular row. This function should be called with row < row_count().

This function does not register dependencies on the current binding. For an equivalent function that tracks dependencies, see ModelExt::row_data_tracked

The implementation should return a reference to its ModelNotify field.

You can return &() if you your Model is constant and does not have a ModelNotify field.

Provided Methods§

Sets the data for a particular row.

This function should be called with row < row_count(), otherwise the implementation can panic.

If the model cannot support data changes, then it is ok to do nothing. The default implementation will print a warning to stderr.

If the model can update the data, it should also call ModelNotify::row_changed on its internal ModelNotify.

Returns an iterator visiting all elements of the model.

Return something that can be downcast’ed (typically self)

This is useful to get back to the actual model from a ModelRc stored in a component.

let handle = ModelRc::new(VecModel::from(vec![1i32, 2, 3]));
// later:
assert_eq!(handle.row_data(3).unwrap(), 4);

Note: the default implementation returns nothing interesting. this method should be implemented by model implementation to return something useful. For example:

fn as_any(&self) -> &dyn core::any::Any { self }

Implementations on Foreign Types§