Struct ProjectionMapper 

pub struct ProjectionMapper {
    pub fields: Vec<FieldMapping>,
    pub typename: Option<String>,
    pub federation_mode: bool,
}

Projection mapper - maps JSONB fields to GraphQL selection set.

Fields

fields: Vec<FieldMapping>

Fields to project (with optional aliases).

typename: Option<String>

Optional __typename value to add to each object.

federation_mode: bool

When true, __typename is injected unconditionally regardless of selection set. Used by federation _entities resolver where the gateway always expects __typename.

Implementations

impl ProjectionMapper

pub fn new(fields: Vec<String>) -> Self

Create new projection mapper from field names (no aliases).

pub const fn with_mappings(fields: Vec<FieldMapping>) -> Self

Create new projection mapper with field mappings (supports aliases).

pub fn with_declared_scalars( self, schema: &CompiledSchema, entity_type: &str, ) -> Self

Mark every mapping whose field entity_type declares as a scalar (#1192), so the JSON-text recovery in FieldMapping::declared_scalar does not fire on a String whose characters happen to be JSON.

Lookup is by the mapping’s output name — the GraphQL field name, which is what a type definition carries — falling back to source for a mapping built from a stored key. A field the schema does not describe stays unmarked: this narrows the recovery to what is positively known, and never widens it.

pub fn with_typename(self, typename: impl Into<String>) -> Self

Set __typename to include in projected objects.

pub const fn with_federation_mode(self, enabled: bool) -> Self

Enable federation mode: __typename is always injected regardless of selection set.

pub fn project(&self, jsonb: &JsonbValue) -> Result<JsonValue>

Project fields from JSONB value.

Arguments

• jsonb - JSONB value from database

Returns

Projected JSON value with only requested fields (and aliases applied)

Errors

Returns error if projection fails.

pub fn project_json_object( &self, map: &Map<String, JsonValue>, ) -> Result<JsonValue>

Project object fields from JSON object.

Maps source keys to output keys according to the configured FieldMappings, injects __typename when configured, and recursively projects nested objects and arrays.

Errors

Returns error if nested value projection fails.

Trait Implementations

impl Clone for ProjectionMapper

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ProjectionMapper

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

Formats the value using the given formatter.