Enum bevy::ecs::query::QueryComponentError

pub enum QueryComponentError {
    MissingReadAccess,
    MissingWriteAccess,
    MissingComponent,
    NoSuchEntity,
}

An error that occurs when retrieving a specific Entity’s component from a Query.

Variants

MissingReadAccess

The Query does not have read access to the requested component.

This error occurs when the requested component is not included in the original query.

Example

fn get_missing_read_access_error(query: Query<&OtherComponent>, res: Res<SpecificEntity>) {
    assert_eq!(
        query.get_component::<RequestedComponent>(res.entity),
        Err(QueryComponentError::MissingReadAccess),
    );
    println!("query doesn't have read access to RequestedComponent because it does not appear in Query<&OtherComponent>");
}

MissingWriteAccess

The Query does not have write access to the requested component.

This error occurs when the requested component is not included in the original query, or the mutability of the requested component is mismatched with the original query.

Example

fn get_missing_write_access_error(mut query: Query<&RequestedComponent>, res: Res<SpecificEntity>) {
    assert_eq!(
        query.get_component::<RequestedComponent>(res.entity),
        Err(QueryComponentError::MissingWriteAccess),
    );
    println!("query doesn't have write access to RequestedComponent because it doesn't have &mut in Query<&RequestedComponent>");
}

MissingComponent

The given Entity does not have the requested component.

NoSuchEntity

The requested Entity does not exist.

Trait Implementations

impl Debug for QueryComponentError

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

Formats the value using the given formatter.

impl Display for QueryComponentError

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

Formats the value using the given formatter.

impl Error for QueryComponentError

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

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 QueryComponentError

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

This method tests for self and other values to be equal, and is used by ==.

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

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

impl Eq for QueryComponentError

impl StructuralEq for QueryComponentError

impl StructuralPartialEq for QueryComponentError