Struct FieldDescriptor 

pub struct FieldDescriptor { /* private fields */ }

A linked, feature-resolved field descriptor.

Constructed only by DescriptorPool; not constructible by downstream crates. The fields are accessed through methods so the pool can change its internal representation without breaking consumers.

Implementations

impl FieldDescriptor

pub fn name(&self) -> &str

Proto field name (as written in the .proto file).

pub fn json_name(&self) -> &str

JSON name — lowerCamelCase unless overridden by [json_name = ...].

pub fn number(&self) -> u32

Field number, in [1, 2^29 - 1].

pub fn kind(&self) -> FieldKind

Resolved kind (scalar/enum/message/list/map).

pub fn presence(&self) -> FieldPresence

Resolved presence discipline. For List/Map kinds this is always Implicit (repeated fields have no presence).

pub fn is_packed(&self) -> bool

Whether a List of packable scalars uses packed wire encoding. Meaningless for non-list or non-packable kinds.

pub fn is_delimited(&self) -> bool

Whether a Message kind uses delimited (group-style) wire encoding. Meaningless for non-message kinds.

pub fn oneof_index(&self) -> Option<u16>

Index into the parent message’s oneofs, if this field belongs to a oneof (including proto3 synthetic oneofs for optional).

pub fn options(&self) -> Option<&FieldOptions>

The raw FieldOptions for this field, if any were declared.

Standard options (deprecated, etc.) read directly off the returned struct. Custom options — [(my.pkg.opt) = ...] — are extensions of google.protobuf.FieldOptions; they survive on the returned struct’s unknown fields. To read one generically, register the option’s defining proto (and descriptor.proto) in the same pool, then reflect over the options via DynamicMessage::from_options:

let dyn_opts = DynamicMessage::from_options(Arc::clone(&pool), field.options()?)?;
let ext = pool.extension_by_name("my.pkg.opt")?;
let value = dyn_opts.get(ext.field());

Trait Implementations

impl AsRef<FieldDescriptor> for ExtensionDescriptor

fn as_ref(&self) -> &FieldDescriptor

Equivalent to field(), for generic code that accepts “anything that is a field descriptor”.

impl Clone for FieldDescriptor

fn clone(&self) -> FieldDescriptor

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FieldDescriptor

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

Formats the value using the given formatter.