pub trait Model {
type Data;
// Required methods
fn row_count(&self) -> usize;
fn row_data(&self, row: usize) -> Option<Self::Data>;
fn model_tracker(&self) -> &dyn ModelTracker;
// Provided methods
fn set_row_data(&self, _row: usize, _data: Self::Data) { ... }
fn iter(&self) -> ModelIterator<'_, Self::Data> ⓘ
where Self: Sized { ... }
fn as_any(&self) -> &(dyn Any + 'static) { ... }
}Expand description
A Model is providing Data for the repeated elements with for in 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.
Properties of type array will be mapped to a ModelRc<T>, which wraps a Rc<Model<Data = T>>.
The ModelRc documentation has examples on how to set models to array properties.
It is more efficient to operate on the model and send changes through the ModelNotify rather than
resetting the property with a different model.
Example
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 {
self.array.borrow().len()
}
fn row_data(&self, row: usize) -> Option<Self::Data> {
self.array.borrow().get(row).cloned()
}
fn set_row_data(&self, row: usize, data: Self::Data) {
self.array.borrow_mut()[row] = data;
// don't forget to call row_changed
self.notify.row_changed(row);
}
fn model_tracker(&self) -> &dyn ModelTracker {
&self.notify
}
fn as_any(&self) -> &dyn core::any::Any {
// a typical implementation just return `self`
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.array.borrow_mut().push(value);
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.array.borrow_mut().remove(index);
self.notify.row_removed(index, 1)
}
}Required Associated Types§
type Data
type Data
The model data: A model is a set of row and each row has this data
Required Methods§
fn row_data(&self, row: usize) -> Option<Self::Data>
fn row_data(&self, row: usize) -> Option<Self::Data>
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
fn model_tracker(&self) -> &dyn ModelTracker
fn model_tracker(&self) -> &dyn ModelTracker
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§
fn set_row_data(&self, _row: usize, _data: Self::Data)
fn set_row_data(&self, _row: usize, _data: Self::Data)
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.
fn iter(&self) -> ModelIterator<'_, Self::Data> ⓘwhere
Self: Sized,
fn iter(&self) -> ModelIterator<'_, Self::Data> ⓘwhere Self: Sized,
Returns an iterator visiting all elements of the model.
fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
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 ItemTree.
let handle = ModelRc::new(VecModel::from(vec![1i32, 2, 3]));
// later:
handle.as_any().downcast_ref::<VecModel<i32>>().unwrap().push(4);
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 }