Struct DataContext

pub struct DataContext<Vertex> { /* private fields */ }

A partial result of a Trustfall query within the interpreter defined in this module.

Implementations

impl<Vertex> DataContext<Vertex>

pub fn active_vertex<V>(&self) -> Option<&V>

where Vertex: AsVertex<V>,

The vertex currently being processed.

For contexts passed to an Adapter resolver method, this is the vertex whose data needs to be resolved.

The active vertex may be None when processing an @optional part of a Trustfall query whose data did not exist. In that case:

• Adapter::resolve_property must produce FieldValue::Null for that context.
• Adapter::resolve_neighbors must produce an empty iterator of neighbors such as Box::new(std::iter::empty()) for that context.
• Adapter::resolve_coercion must produce a false coercion outcome for that context.

pub fn map<Other>( self, mapper: &mut impl FnMut(Vertex) -> Other, ) -> DataContext<Other>

Converts DataContext<Vertex> to DataContext<Other> by mapping each Vertex to Other.

If you are implementing an Adapter for a data source, you almost certainly should not be using this function. You’re probably looking for DataContext::active_vertex() instead.

pub fn flat_map<T>( self, mapper: &mut impl FnMut(Vertex) -> Option<T>, ) -> DataContext<T>

Map each Vertex to Option<Other>, thus converting Self to DataContext<Other>.

This is the DataContext equivalent of Option::and_then, which is also referred to as “flat-map” in some languages.

If you are implementing an Adapter for a data source, you almost certainly should not be using this function. You’re probably looking for DataContext::active_vertex() instead.

impl<Vertex> DataContext<Vertex>

where Vertex: Clone + Debug,

pub fn new(vertex: Option<Vertex>) -> DataContext<Vertex>

Trait Implementations

impl<Vertex> Clone for DataContext<Vertex>

where Vertex: Clone,

fn clone(&self) -> DataContext<Vertex>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<Vertex> Debug for DataContext<Vertex>

where Vertex: Debug,

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

Formats the value using the given formatter.

impl<'de, Vertex> Deserialize<'de> for DataContext<Vertex>

where Vertex: Debug + Clone + Serialize + DeserializeOwned,

fn deserialize<D>( deserializer: D, ) -> Result<DataContext<Vertex>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<Vertex> From<SerializableContext<Vertex>> for DataContext<Vertex>

fn from(context: SerializableContext<Vertex>) -> DataContext<Vertex>

Converts to this type from the input type.

impl<Vertex> PartialEq for DataContext<Vertex>

where Vertex: PartialEq,

fn eq(&self, other: &DataContext<Vertex>) -> 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<Vertex> Serialize for DataContext<Vertex>

where Vertex: Debug + Clone + Serialize + DeserializeOwned,

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<Vertex> Eq for DataContext<Vertex>

where Vertex: Eq,