Struct SystemParamValidationError

pub struct SystemParamValidationError {
    pub skipped: bool,
    pub message: Cow<'static, str>,
    pub param: Cow<'static, str>,
    pub field: Cow<'static, str>,
}

An error that occurs when a system parameter is not valid, used by system executors to determine what to do with a system.

Returned as an error from SystemParam::validate_param, and handled using the unified error handling mechanisms defined in bevy_ecs::error.

Fields

skipped: bool

Whether the system should be skipped.

If false, the error should be handled. By default, this will result in a panic. See crate::error for more information.

This is the default behavior, and is suitable for system params that should always be valid, either because sensible fallback behavior exists (like Query or because failures in validation should be considered a bug in the user’s logic that must be immediately addressed (like Res).

If true, the system should be skipped. This is suitable for system params that are intended to only operate in certain application states, such as Single.

message: Cow<'static, str>

A message describing the validation error.

param: Cow<'static, str>

A string identifying the invalid parameter. This is usually the type name of the parameter.

field: Cow<'static, str>

A string identifying the field within a parameter using #[derive(SystemParam)]. This will be an empty string for other parameters.

This will be printed after param in the Display impl, and should include a :: prefix if non-empty.

Implementations

impl SystemParamValidationError

pub fn skipped<T>(message: impl Into<Cow<'static, str>>) -> Self

Constructs a SystemParamValidationError that skips the system. The parameter name is initialized to the type name of T, so a SystemParam should usually pass Self.

pub fn invalid<T>(message: impl Into<Cow<'static, str>>) -> Self

Constructs a SystemParamValidationError for an invalid parameter that should be treated as an error. The parameter name is initialized to the type name of T, so a SystemParam should usually pass Self.

pub fn new<T>( skipped: bool, message: impl Into<Cow<'static, str>>, field: impl Into<Cow<'static, str>>, ) -> Self

Constructs a SystemParamValidationError for an invalid parameter. The parameter name is initialized to the type name of T, so a SystemParam should usually pass Self.

Trait Implementations

impl Clone for SystemParamValidationError

fn clone(&self) -> SystemParamValidationError

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for SystemParamValidationError

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

Formats the value using the given formatter.

impl Display for SystemParamValidationError

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

Formats the value using the given formatter.

impl Error for SystemParamValidationError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for SystemParamValidationError

fn eq(&self, other: &SystemParamValidationError) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for SystemParamValidationError

impl StructuralPartialEq for SystemParamValidationError