Oihana PHP Arango

resolveEdgeTarget.php

Table of Contents

Functions

resolveEdgeTarget()  : Documents|null
Resolves the vertex model a traversal reaches — the model whose fields are projected, whose `Field::REQUIRES` gate the projection, and whose own relations the walk continues through.

Functions

resolveEdgeTarget()

Resolves the vertex model a traversal reaches — the model whose fields are projected, whose `Field::REQUIRES` gate the projection, and whose own relations the walk continues through.

resolveEdgeTarget(Edges $model, string $direction) : Documents|null

An edge has two ends, and the direction says which one the walk lands on: INBOUND reaches the _from model, OUTBOUND the _to model. That much was already written, three times, as a binary ternary — and a binary ternary has no room for the third keyword:

$documents = $direction == Traversal::INBOUND ? $model->from : $model->to ; // ANY silently lands on `to`

Traversal::ANY reaches both ends, so on a heterogeneous relation no single model describes what comes back: the vertices of the far side were projected with the near side's fields and, worse, gated by the near side's permissions — a field masked on one collection served through the other. It is therefore refused rather than resolved to half of it.

ANY stays perfectly valid where it is meaningful — a self-referential relation, both ends on the same collection (user_follows, a thesaurus), which is the case it exists for. It then keeps resolving to the _to end, the one the ternary picked, so an unambiguous declaration compiles byte for byte as before. Both ends being unwired is left alone too: the model declares no vertex model at all, and the callers that tolerate that keep their behaviour.

Parameters
$model : Edges

The edge model carrying the two vertex ends.

$direction : string

A validated Traversal keyword, as returned by resolveEdgeDirection().

Tags
throws
UnexpectedValueException

When ANY cannot designate a single reached model.

example 
use function oihana\arango\models\helpers\edges\resolveEdgeTarget;

resolveEdgeTarget( $articlesAuthors , Traversal::OUTBOUND ) ; // the `authors` model
resolveEdgeTarget( $articlesAuthors , Traversal::INBOUND  ) ; // the `articles` model
resolveEdgeTarget( $userFollows     , Traversal::ANY      ) ; // the `users` model (both ends)
resolveEdgeTarget( $articlesAuthors , Traversal::ANY      ) ; // throws — two different ends
since
1.7.0
author

Marc Alcaraz

Return values
Documents|null —

The reached vertex model, or null when that end is not wired.

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