Enum Change 

#[non_exhaustive]
pub enum Change<'a, E> {
    Created {
        after: &'a mut E,
    },
    Updated {
        before: &'a E,
        after: &'a mut E,
    },
    Transitioned {
        before: &'a E,
        after: &'a mut E,
        transition: String,
        field: String,
        from: Option<String>,
        to: Option<String>,
    },
    Deleted {
        before: &'a E,
        hard: bool,
    },
    Restored {
        entity: &'a E,
    },
}

One row change, as a write hook sees it.

In WriteHooks::before the row to be stored is mutable: a hook may fill a derived field. In WriteHooks::after it is the row as stored. Matching on it needs a wildcard arm; kinds may be added.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Created

A row is created.

Fields

after: &'a mut E

The row to store, or as stored.

Updated

A row is changed by a generic write (PUT, PATCH or their bulk forms).

Fields

before: &'a E

The row as it was read.

after: &'a mut E

The row to store, or as stored.

Transitioned

A row is moved by a state-machine verb.

Fields

before: &'a E

The row as it was read.

after: &'a mut E

The row to store, or as stored.

transition: String

The verb (close, approve).

field: String

The state field that moved, in the serialized naming (status).

from: Option<String>

The state the row left.

to: Option<String>

The state the row entered.

Deleted

A row is deleted: soft-deleted, or removed for good when hard.

Fields

before: &'a E

The row as it was read.

hard: bool

Whether the row is removed for good (from the trash) rather than moved to it.

Restored

A soft-deleted row is restored.

Fields

entity: &'a E

The row: as it was in the trash before the write, as restored after it.

Implementations

impl<'a, E> Change<'a, E>

pub fn kind(&self) -> ChangeKind

Which kind of change this is.

pub fn before(&self) -> Option<&E>

The row as it was read before the write; None for a create.

pub fn after(&self) -> Option<&E>

The row the write stores; None for a delete.

pub fn subject(&self) -> &E

The row an event of this change is about: what the write stores, or the row deleted.

impl<'a, E> Change<'a, E>

pub fn after_mut(&mut self) -> Option<&mut E>

The row to store, mutable: for a hook that fills a field before the write. None for a delete or a restore, which store no new row.

pub fn before_and_after_mut(&mut self) -> Option<(&E, &mut E)>

The row as it was read and the row to store, the second mutable: for a hook that fills a field of an update from what it was. None unless the change is an update.

impl<'a, E: Serialize> Change<'a, E>

pub fn field_changed(&self, name: &str) -> bool

Whether the serialized field name differs between the row before and after. A create changes every field it sets (non-null); a delete changes none.

Trait Implementations

impl<'a, E: Debug> Debug for Change<'a, E>

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

Formats the value using the given formatter.