classDocs / Mixin

Mixin

classsharedsource

Object → Mixin

A mixin is an ordered chain of transformer functions.

Each handler in the chain receives the previous (old_value) and current (new_value) values plus any extra arguments, and may return a new value to replace new_value for the next handler in the chain.

Mixins are themselves callable and can be nested inside one another as handlers.

Constructor

Mixin(name: ( string | nil )): Mixin

Fields

Name	Type	Description
`name`	`string`	The name of the mixin.

Methods

`attach`	Attaches a handler (or nested Mixin) to the end of the chain.
`call`	Runs every handler in the chain in order, passing each one the running old_value/new_value pair plus any extra argument…
`detach`	Detaches a previously attached handler from the chain.

#Mixin:attach

sharedsource

function Mixin:attach(mixer: ( fun( old_value: ( T | nil ), new: T, ...: any ): ( T | nil ) ) | Mixin<T>): integer

Attaches a handler (or nested Mixin) to the end of the chain. If the handler is already attached, it is moved to the end instead of being added twice.

Throws if mixer is not callable, or if attaching it would create a cycle (a Mixin that indirectly contains self).

Parameters

Name	Type	Description
`mixer`	`( fun( old_value: ( T \| nil ), new: T, ...: any ): ( T \| nil ) ) \| Mixin<T>`	The handler to attach.

Returns

Type	Name	Description
`integer`	`depth`	The handler's position in the chain after attaching.

#Mixin:call

sharedsource

function Mixin:call(old_value: T | nil, new_value: T, ...: any): T

Runs every handler in the chain in order, passing each one the running old_value/new_value pair plus any extra arguments.

Any handler that returns a non-nil result becomes the new new_value for the next handler (with the previous new_value shifted into old_value).

Throws if any handler errors.

Parameters

Name	Type	Description
`old_value`	`T \| nil`	The previous value, if any.
`new_value`	`T`	The current value to transform.
`...`	`any`	Extra arguments forwarded to every handler.

Returns

Type	Name	Description
`T`	`new_value`	The final value after all handlers have run.

#Mixin:detach

sharedsource

function Mixin:detach(mixer: ( fun( old_value: ( T | nil ), new: T, ...: any ): ( T | nil ) ) | Mixin<T>): boolean

Detaches a previously attached handler from the chain.

Parameters

Name	Type	Description
`mixer`	`( fun( old_value: ( T \| nil ), new: T, ...: any ): ( T \| nil ) ) \| Mixin<T>`	The exact handler reference that was previously passed to `attach`.

Returns

Type	Name	Description
`boolean`	`is_detached`	Returns `true` if the handler was found and detached, otherwise `false`.