Struct DataSource

pub struct DataSource(/* private fields */);

Use data sources to separate the user interface from the application data and to remove the dependencies between a Kanzi Studio project and the application code which define the Kanzi application. Kanzi allows you to define the format and structure of your data source by defining a Kanzi Engine data source plugin.

When you use a data source in a Kanzi application you bind the values of properties and property fields to data that comes from a data source. This binding establishes a connection between a node or a resource and the application data. When data in the data source changes, the nodes and resources which are bound to the data reflect the change in the data.

To set a node to use a data source, use the DataContext::DataContext property. When you set the Data Context property for a node, all its child nodes inherit the value of the Data Context property. After you set a node to use a data source, you can use bindings to access the data. See DataSourceBindingSource and DataSourceExpressionValueSource.

Set the value of the DataContext::DataContext property to one of these:

• Uri that defines the resource.

• %Resource ID that defines the resource in a resource dictionary.

• Path that allows to navigate further within the current data context. For example:

  $.car.cluster

The format of a data context binding is:

{DataContext.path.to.data}

For example:

{DataContext.car.cluster.speed}

Data context bindings support all standard Kanzi binding features, such as expressions.

Methods from Deref<Target = DataContext>

pub fn get_data_context(&self) -> Result<Option<Weak<Resource>>, Error>

See: DATA_CONTEXT_PROPERTY

pub fn set_data_context(&self, value: Option<&Resource>) -> Result<(), Error>

See: DATA_CONTEXT_PROPERTY

pub fn get_items_source(&self) -> Result<Option<Weak<Resource>>, Error>

See: ITEMS_SOURCE_PROPERTY

pub fn set_items_source(&self, value: Option<&Resource>) -> Result<(), Error>

See: ITEMS_SOURCE_PROPERTY

pub fn add_modified_notification_handler( &self, callback: impl Handle, ) -> Result<ModifiedSubscriptionToken, Error>

Allows to subscribe to modifications in this data context.

Arguments

• callback - Callback that is invoked when a change occurs in this data context.

Returns

Token that can be used to identify and remove given subscription.

pub fn remove_modified_notification_handler( &self, token: &ModifiedSubscriptionToken, ) -> Result<(), Error>

Allows to unsubscribe from modifications in this data context.

Arguments

• token - Token to identify the subscription that should be removed.

pub fn notify_modified(&self) -> Result<(), Error>

Triggers modification procedure in this data context, which invokes the subscriptions. Should be called by derived classes whenever the value of the object is changed.

pub fn get_data(&self) -> Result<Option<Weak<DataObject<()>>>, Error>

Retrieves the root object of the underlying data tree. Needs to be implemented by the derived class.

Returns

Returns data object that is the root of the data tree.

pub fn lookup_data_context( &self, relative_path: impl AsRef<KanziStr>, ) -> Result<Option<Weak<DataContext>>, Error>

Performs object look-up by path.

Arguments

• relative_path - Path of the object where to look at, separated by ‘.’.

Returns

Data object that was found, or empty pointer if there was no such object.

Methods from Deref<Target = Resource>

pub fn get_name(&self) -> Result<KanziString, Error>

Gets the resource name.

pub fn get_url(&self) -> Result<KanziString, Error>

Gets the resource URL. Note that the URL is not necessarily in URL form if resource has been just created.

Returns

URL string.

pub fn set_keep_alive(&self, keep_alive: bool) -> Result<(), Error>

Sets the keep alive flag. Can be set only before the resource is registered to the resource manager. Normally set by loadFromKZB.

Arguments

• keep_alive - Value for the keep alive flag.

Methods from Deref<Target = Object>

pub fn as_ptr(&self) -> *mut ObjectWrapper

pub fn as_wrapper(&self) -> &ObjectWrapper

pub fn as_object(&self) -> &Object

Represents any type inheriting from Object as &Object. This is useful for comparisions when PartialEq traits failed to compare objects of different types.

let child = screen.get_child(0)?;
let parent = child.get_parent()?.into_error(ErrorKind::ObjectNotFound)?;
// assert_eq!(screen, parent); // <- Fails to compile!
assert_eq!(screen.as_object(), parent.as_object());

pub fn get_native(&self) -> Result<NonNull<c_void>, Error>

Gets a pointer to the backing C++ instance.

pub fn is_stale(&self) -> bool

Checks whether the weak reference has expired.

pub fn get_property<T>( &self, property_type: &PropertyType<T>, ) -> Result<<T as VariantConstraint>::RetArg, Error>

where T: PropertyTypeConstraint,

Returns the current value of a property disregarding modifiers.

Base value is affected by the following inputs where the highest entry in the list determines the base value:

1. Local value set with setProperty or loaded from kzb
2. Value set by a style affecting the property.
3. Value defined by class metadata.

Modifiers are not applied, the highest-priority base value is returned.

If no inputs to the property value can be established the system returns the value default value from property type metadata.

Arguments

• property_type - The property type identifying the property to retrieve.

Returns

The evaluated property value.

pub fn get_optional_property<T>( &self, property_type: &PropertyType<T>, ) -> Result<Option<<T as VariantConstraint>::RetArg>, Error>

where T: PropertyTypeConstraint,

Returns the current value of a property disregarding modifiers, but does not default to the value in property metadata if there are no inputs to the property value.

If there is no value sources, None is returned.

If no inputs to the property value can be established the system returns the value default value from property type metadata.

Arguments

• property_type - The property type identifying the property to retrieve.

Returns

The evaluated property value.

pub fn set_property<T>( &self, property_type: &PropertyType<T>, value: <T as VariantConstraint>::DataArg<'_>, ) -> Result<(), Error>

where T: PropertyTypeConstraint,

Sets the local value of a property type.

pub fn has_value<T>( &self, property_type: &PropertyType<T>, ) -> Result<bool, Error>

where T: PropertyTypeConstraint,

Evaluates whether there are any inputs into the property value. Both value sources and modifiers are taken into account.

Returns

Returns true if there are inputs into the property value, false otherwise.

pub fn remove_local_value<T>( &self, property_type: &PropertyType<T>, ) -> Result<(), Error>

where T: PropertyTypeConstraint,

Removes the local value associated with the property.

pub fn get_metaclass(&self) -> Result<Metaclass, Error>

Returns the metaclass of the dynamic type of the object.

pub fn get_domain(&self) -> Result<Domain, Error>

Returns the domain the object belongs to.

pub fn set_flag_keep_during_patching<T>( &self, property_type: &PropertyType<T>, ) -> Result<(), Error>

where T: PropertyTypeConstraint,

Sets the flag to indicate that the property was loaded from KZB.

pub fn debug_string(&self) -> Result<String, Error>

Builds a string representation of the object intended for debugging purposes.

Trait Implementations

impl Clone for DataSource

fn clone(&self) -> DataSource

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DataSource

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

Formats the value using the given formatter.

impl Deref for DataSource

type Target = DataContext

The resulting type after dereferencing.

fn deref(&self) -> &<DataSource as Deref>::Target

Dereferences the value.

impl Inheritable for DataSource

unsafe fn downcast_unchecked<T>(self) -> T

where T: Inherits<Self>,

Downcast the object to a more specific type.

unsafe fn downcast_unchecked_ref<T>(&self) -> &T

where T: Inherits<Self>,

Downcast the object reference to a more specific type.

impl Inherits<DataContext> for DataSource

fn upcast(self) -> Base

fn upcast_ref(&self) -> &Base

impl Inherits<Object> for DataSource

fn upcast(self) -> Base

fn upcast_ref(&self) -> &Base

impl Inherits<Resource> for DataSource

fn upcast(self) -> Base

fn upcast_ref(&self) -> &Base

impl MetaclassConstraint for DataSource

fn get_static_metaclass() -> &'static Metaclass

Gets metaclass associated with a given type.

impl ObjectConstraint for DataSource

fn downcast<T>(self) -> Result<Option<T>, Error>

where T: MetaInherits<Self>,

Casts metaclass to a more specific type by value.

fn downcast_ref<T>(&self) -> Result<Option<&T>, Error>

where T: MetaInherits<Self>,

Casts metaclass to a more specific type by reference.

fn is_a<T>(&self) -> Result<bool, Error>

where T: MetaInherits<Self>,

Determines whether the class this metaclass describes derives from a class described by specified metaclass.

fn downgrade(self) -> Weak<Self>

fn downgrade_ref(&self) -> Weak<Self>

fn lock(self) -> ThreadObject<Self>

fn lock_ref(&self) -> ThreadObject<Self>

impl<T> PartialEq<T> for DataSource

where T: ObjectConstraint,

fn eq(&self, rhs: &T) -> bool

Tests for self and other values to be equal, and is used by ==.

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

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

impl<T> PartialEq<Weak<T>> for DataSource

where T: ObjectConstraint,

fn eq(&self, rhs: &Weak<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

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

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

impl Eq for DataSource