Flag

A flag lets you add a marker on an entity after its creation. Its purpose is to indicate that a verification has taken place, or that a particular operation has been performed, without modifying the structure of the entity.

Example

How it works

C.createFlag(...) returns a flag handler. This handler allows:

• adding the flag to an entity via append(...)
• retrieving the associated value (optional) via getValue(...)
• checking if the flag is present via has(...)

Once the flag is added, the entity typing is enriched: you can require Entity & MyFlag in a function, to ensure that a business step has indeed been performed.

Create a flag

Creating a flag means defining:

• which entity it applies to
• its name (key stored on the entity)
• an optional value associated with the flag (useful to carry a computed piece of data)

Methods and Properties

A FlagHandler exposes:

Methods

append()

Adds the flag to the entity and returns an entity enriched with the flag type.

function append(
	entity: Entity
): Entity & Flag<FlagName>

If the flag carries a value, append also expects this value:

function append(
	entity: Entity,
	value: FlagValue
): Entity & Flag<FlagName, FlagValue>

getValue()

Retrieves the value associated with the flag.

function getValue(
	entity: Entity & Flag<FlagName, FlagValue>
): FlagValue

has()

Checks whether the flag is present on the entity.

function has(
	entity: Entity
): boolean

Properties

name

The unique name of the flag (the key stored on the entity).

Get the type

type MajorFlag = C.GetFlag<typeof MajorFlag>;

See also

• entity
• newType