Struct PinnedRelation 

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

Reference to the exact version of the document.

PinnedRelation pin a relation to a specific, immutable version of a document or many documents when necessary (PinnedRelation or PinnedRelationList).

When the blog post from the Relation example changes its contents from Monday evening to Tuesday morning the comment would automatically refer to the new version as the comment refers to the document as a whole, including all future changes.

Since the comment was probably meant to be referring to Monday when it was created, we have to pin it to the exact version of the blog post in order to preserve this meaning. A PinnedRelation achieves this by referring to the blog post’s document view id:

                   Document-View                              Document-View
                        |                                           |
Document: [Blog-Post "Monday evening"] -- UPDATE -- > [Blog-Post "Tuesday morning"]
                  ^
                  |
     _____________|  Pinned Relation (we will stay in the "past")
    |
    |
Document: [Comment "This was great!"]

Document view ids contain the operation ids of the document graph tips, which is all the information we need to reliably recreate the document at this certain point in time.

Pinned relations give us immutability and the option to restore a historical state across documents. However, most cases will probably only need unpinned relations: For example when referring to a user-profile you probably want to always get the latest version.

Implementations

impl PinnedRelation

pub fn new(document_view_id: DocumentViewId) -> Self

Returns a new pinned relation field.

pub fn view_id(&self) -> &DocumentViewId

Returns the pinned relation’s document view id.

pub fn iter(&self) -> Iter<'_, OperationId>

Returns iterator over operation ids.

Trait Implementations

impl Clone for PinnedRelation

fn clone(&self) -> PinnedRelation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PinnedRelation

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for PinnedRelation

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for PinnedRelation

fn eq(&self, other: &PinnedRelation) -> 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 Serialize for PinnedRelation

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Validate for PinnedRelation

type Error = PinnedRelationError

Validation error type.

fn validate(&self) -> Result<(), Self::Error>

Validates p2panda data type instance.

impl Eq for PinnedRelation

impl StructuralPartialEq for PinnedRelation