Subscription

Represents a disposable resource, such as the execution of an Observable. A Subscription has one important method, unsubscribe, that takes no argument and just disposes the resource held by the subscription.

class Subscription implements SubscriptionLike {
  static EMPTY: (() => {...})
  constructor(initialTeardown?: () => void)
  closed: false
  unsubscribe(): void
  add(teardown: TeardownLogic): void
  remove(teardown: Subscription | Unsubscribable | (() => void)): void
}

Description

Additionally, subscriptions may be grouped together through the add() method, which will attach a child Subscription to the current Subscription. When a Subscription is unsubscribed, all its children (and its grandchildren) will be unsubscribed as well.

Static Properties

Property	Type	Description
EMPTY	(() => { const empty = new Subscription(); empty.closed = true; return empty; })()

Constructor

constructor(initialTeardown?: () => void)

Parameters

initialTeardown

Optional. Default is undefined. A function executed first as part of the teardown process that is kicked off when unsubscribe is called.

Properties

Property	Type	Description
closed	false	A flag to indicate whether this Subscription has already been unsubscribed.

Methods

unsubscribe(): void

Disposes the resources held by the subscription. May, for instance, cancel an ongoing Observable execution or cancel any other type of work that started when the Subscription was created.

Parameters

There are no parameters.

Returns

void:

add(teardown: TeardownLogic): void

Adds a teardown to this subscription, so that teardown will be unsubscribed/called when this subscription is unsubscribed. If this subscription is already closed, because it has already been unsubscribed, then whatever teardown is passed to it will automatically be executed (unless the teardown itself is also a closed subscription).

Parameters

teardown

The teardown logic to add to this subscription.

Returns

void

Closed Subscriptions cannot be added as teardowns to any subscription. Adding a closed subscription to a any subscription will result in no operation. (A noop).

Adding a subscription to itself, or adding null or undefined will not perform any operation at all. (A noop).

Subscription instances that are added to this instance will automatically remove themselves if they are unsubscribed. Functions and Unsubscribable objects that you wish to remove will need to be removed manually with remove

remove(teardown: Subscription | Unsubscribable | (() => void)): void

Removes a teardown from this subscription that was previously added with the add method.

Parameters

teardown

The teardown to remove from this subscription

Returns

void

Note that Subscription instances, when unsubscribed, will automatically remove themselves from every other Subscription they have been added to. This means that using the remove method is not a common thing and should be used thoughtfully.

If you add the same teardown instance of a function or an unsubscribable object to a Subcription instance more than once, you will need to call remove the same number of times to remove all instances.

All teardown instances are removed to free up memory upon unsubscription.