Struct Precondition 

pub struct Precondition {
    pub if_match: Option<StateEtag>,
    pub expected_generation: Option<u64>,
}

Optimistic-concurrency precondition for a mutating request (#1). A request may pin the prior ETag (If-Match), the prior generation, or both. An empty precondition is an unconditional write (creates only — see the contract doc).

Fields

if_match: Option<StateEtag>

expected_generation: Option<u64>

Implementations

impl Precondition

pub fn matching(etag: StateEtag, generation: u64) -> Self

Pin both the ETag and generation of the resource as currently observed.

pub fn is_conditional(&self) -> bool

True if the precondition pins prior state (an If-Match and/or an expected generation). An empty precondition pins nothing.

pub fn check( &self, current_etag: &StateEtag, current_generation: u64, ) -> Result<(), PreconditionError>

Check the precondition against the server’s current state for a guarded (update/restore/delete) write.

An empty precondition is rejected with PreconditionError::Required rather than silently passing — a conditional write must pin prior state, otherwise a stale or malformed client clobbers a newer generation. The create-if-absent path does not call check; it is gated by an existence check on the server (see the contract doc).

Trait Implementations

impl Clone for Precondition

fn clone(&self) -> Precondition

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Precondition

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

Formats the value using the given formatter.

impl Default for Precondition

fn default() -> Precondition

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Precondition

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for Precondition

impl PartialEq for Precondition

fn eq(&self, other: &Precondition) -> 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 Serialize for Precondition

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Precondition