Struct ParameterDescriptor 

pub struct ParameterDescriptor {
    pub name: String<MAX_PARAM_NAME_LEN>,
    pub param_type: ParameterType,
    pub description: String<MAX_PARAM_DESCRIPTION_LEN>,
    pub additional_constraints: String<MAX_PARAM_CONSTRAINTS_LEN>,
    pub read_only: bool,
    pub dynamic_typing: bool,
    pub range: ParameterRange,
    /* private fields */
}

Parameter descriptor containing metadata

Describes a parameter including its type, constraints, and documentation.

Fields

name: String<MAX_PARAM_NAME_LEN>

Parameter name

param_type: ParameterType

Parameter type

description: String<MAX_PARAM_DESCRIPTION_LEN>

Human-readable description.

phase-446 F2 – its own capacity, NROS_MAX_PARAM_DESCRIPTION_LEN. It used to share MAX_STRING_VALUE_LEN, which the contract derives to 0 for an image with no string parameter, so such an image could carry no description at all. Write it with Self::set_description, which truncates and records the truncation instead of dropping the text.

additional_constraints: String<MAX_PARAM_CONSTRAINTS_LEN>

Free-text extra constraints — rcl_interfaces/msg/ParameterDescriptor’s additional_constraints, which ros2 param describe prints.

phase-417 W4.a — its own capacity, NROS_MAX_PARAM_CONSTRAINTS_LEN, default 0. Sharing the description’s knob was the first shape and the derived service buffer measured it wrong: the describe reply’s bound is a worst case over CAPACITY, not over use, so every image would have paid 256 bytes per parameter for a field it never sets — 2,048 bytes on the eight-parameter island, taking its reply past the 4,096 fallback. An image that wants constraint text states the knob. Write it with Self::set_additional_constraints, which truncates at a character boundary and records the truncation exactly as the description does, so a value that does not fit is reported rather than dropped in silence.

read_only: bool

Whether the parameter is read-only

dynamic_typing: bool

Whether the parameter type can change dynamically

range: ParameterRange

Range constraints

Implementations

impl ParameterDescriptor

pub fn new(name: &str, param_type: ParameterType) -> Option<Self>

Create a new parameter descriptor

pub fn with_description(self, desc: &str) -> Self

Set the description. A description longer than NROS_MAX_PARAM_DESCRIPTION_LEN is truncated at a character boundary and recorded (see Self::set_description).

pub fn set_description(&mut self, desc: &str) -> bool

phase-446 F2 – set the description, truncating at a character boundary when it is longer than NROS_MAX_PARAM_DESCRIPTION_LEN. Returns whether it was truncated; the descriptor also remembers it, so the executor can report it once the parameter is declared.

pub fn description_truncated(&self) -> bool

Whether the last description set was truncated and not yet reported.

pub fn set_additional_constraints(&mut self, text: &str) -> bool

phase-417 W4.a — rclc’s additional_constraints, the fourth argument of rclc_add_parameter_description. Truncated and recorded like the description; returns whether anything was cut.

pub fn with_additional_constraints(self, text: &str) -> Self

Builder form of Self::set_additional_constraints.

pub fn with_read_only(self, read_only: bool) -> Self

Set read-only flag

pub fn with_dynamic_typing(self, dynamic: bool) -> Self

Set dynamic typing flag

pub fn with_integer_range(self, min: i64, max: i64, step: i64) -> Self

Set integer range constraints

pub fn with_float_range(self, min: f64, max: f64, step: f64) -> Self

Set floating point range constraints

pub fn validate_range(&self, value: &ParameterValue) -> bool

Check if a value satisfies the range constraints — min, max AND step.

Forwards to ParameterRange::contains, the single predicate.

Trait Implementations

impl Clone for ParameterDescriptor

fn clone(&self) -> ParameterDescriptor

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ParameterDescriptor

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

Formats the value using the given formatter.