Struct zng::var::ContextInitHandle

pub struct ContextInitHandle(/* private fields */);

Identifies the unique context a ContextualizedVar is in.

Each node that sets context-vars have an unique ID, it is different after each (re)init. The ContextualizedVar records this ID, and rebuilds when it has changed. The contextualized inner vars are retained when the ID has at least one clone.

Implementations

impl ContextInitHandle

pub fn new() -> ContextInitHandle

Generates a new unique handle.

pub fn current() -> ContextInitHandle

Gets the current context handle.

pub fn with_context<R>(&self, action: impl FnOnce() -> R) -> R

Runs action with self as the current context ID.

Note that ContextVar::with_context already calls this method.

pub fn downgrade(&self) -> WeakContextInitHandle

Create a weak handle that can be used to monitor self, but does not hold it.

Trait Implementations

impl Clone for ContextInitHandle

fn clone(&self) -> ContextInitHandle

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ContextInitHandle

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

Formats the value using the given formatter.

impl Default for ContextInitHandle

fn default() -> ContextInitHandle

Returns the “default value” for a type.

impl Hash for ContextInitHandle

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for ContextInitHandle

fn eq(&self, other: &ContextInitHandle) -> 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 ContextInitHandle