Oihana PHP Arango

resolveEdgeDirection.php

Table of Contents

Functions

resolveEdgeDirection()  : string
Resolves the traversal direction of an edge relation: which way its edges are followed from the document that declares them.

Functions

resolveEdgeDirection()

Resolves the traversal direction of an edge relation: which way its edges are followed from the document that declares them.

resolveEdgeDirection(array<string|int, mixed> $definition) : string

The direction is not a detail of the AQL — it decides whether the traversal finds anything at all. A relation whose edges leave the document (doc is the _from) reaches its vertices OUTBOUND; one whose edges point at it reaches them INBOUND. Follow the wrong way and the traversal is perfectly valid and matches nothing, so the relation projects an empty array in 200 without a word.

Two rules, and each is deliberate:

  • the default is Traversal::OUTBOUND, which every edge surface of the library already applies — the projection, the count, the grouped dimension, the hierarchical filters, the tree helpers and the write path;
  • an unknown value is refused, never quietly replaced. Traversal::get() was used here before, and it falls back on its default when it does not recognise a value: a mistyped 'OUTBOUD' compiled to OUTBOUND without a word, so a typo on an inbound relation produced exactly the empty projection the option exists to prevent. Traversal::validate() answers instead.

A malformed declaration is a server-side mistake, so it is loud. A key coming from the request is a different matter and keeps being dropped in silence — the frontier the library draws everywhere else.

Parameters
$definition : array<string|int, mixed>

The relation definition. Reads AQL::DIRECTION.

Tags
throws
ConstantException

When the declared direction is not a Traversal keyword.

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

resolveEdgeDirection( [] ) ;                                        // 'OUTBOUND' (the default)
resolveEdgeDirection( [ AQL::DIRECTION => Traversal::INBOUND ] ) ;  // 'INBOUND'
resolveEdgeDirection( [ AQL::DIRECTION => 'OUTBOUD' ] ) ;           // throws
since
1.7.0
author

Marc Alcaraz

Return values
string —

The validated direction keyword.

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