es6/Subscription.js

import { isArray } from './util/isArray';
import { isObject } from './util/isObject';
import { isFunction } from './util/isFunction';
import { tryCatch } from './util/tryCatch';
import { errorObject } from './util/errorObject';
import { UnsubscriptionError } from './util/UnsubscriptionError';
/**
 * 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.
 *
 * 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.
 *
 * @class Subscription
 */
export class Subscription {
    /**
     * @param {function(): void} [unsubscribe] A function describing how to
     * perform the disposal of resources when the `unsubscribe` method is called.
     */
    constructor(unsubscribe) {
        /**
         * A flag to indicate whether this Subscription has already been unsubscribed.
         * @type {boolean}
         */
        this.closed = false;
        this._parent = null;
        this._parents = null;
        this._subscriptions = null;
        if (unsubscribe) {
            this._unsubscribe = unsubscribe;
        }
    }
    /**
     * 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.
     * @return {void}
     */
    unsubscribe() {
        let hasErrors = false;
        let errors;
        if (this.closed) {
            return;
        }
        let { _parent, _parents, _unsubscribe, _subscriptions } = this;
        this.closed = true;
        this._parent = null;
        this._parents = null;
        // null out _subscriptions first so any child subscriptions that attempt
        // to remove themselves from this subscription will noop
        this._subscriptions = null;
        let index = -1;
        let len = _parents ? _parents.length : 0;
        // if this._parent is null, then so is this._parents, and we
        // don't have to remove ourselves from any parent subscriptions.
        while (_parent) {
            _parent.remove(this);
            // if this._parents is null or index >= len,
            // then _parent is set to null, and the loop exits
            _parent = ++index < len && _parents[index] || null;
        }
        if (isFunction(_unsubscribe)) {
            let trial = tryCatch(_unsubscribe).call(this);
            if (trial === errorObject) {
                hasErrors = true;
                errors = errors || (errorObject.e instanceof UnsubscriptionError ?
                    flattenUnsubscriptionErrors(errorObject.e.errors) : [errorObject.e]);
            }
        }
        if (isArray(_subscriptions)) {
            index = -1;
            len = _subscriptions.length;
            while (++index < len) {
                const sub = _subscriptions[index];
                if (isObject(sub)) {
                    let trial = tryCatch(sub.unsubscribe).call(sub);
                    if (trial === errorObject) {
                        hasErrors = true;
                        errors = errors || [];
                        let err = errorObject.e;
                        if (err instanceof UnsubscriptionError) {
                            errors = errors.concat(flattenUnsubscriptionErrors(err.errors));
                        }
                        else {
                            errors.push(err);
                        }
                    }
                }
            }
        }
        if (hasErrors) {
            throw new UnsubscriptionError(errors);
        }
    }
    /**
     * Adds a tear down to be called during the unsubscribe() of this
     * Subscription.
     *
     * If the tear down being added is a subscription that is already
     * unsubscribed, is the same reference `add` is being called on, or is
     * `Subscription.EMPTY`, it will not be added.
     *
     * If this subscription is already in an `closed` state, the passed
     * tear down logic will be executed immediately.
     *
     * @param {TeardownLogic} teardown The additional logic to execute on
     * teardown.
     * @return {Subscription} Returns the Subscription used or created to be
     * added to the inner subscriptions list. This Subscription can be used with
     * `remove()` to remove the passed teardown logic from the inner subscriptions
     * list.
     */
    add(teardown) {
        if (!teardown || (teardown === Subscription.EMPTY)) {
            return Subscription.EMPTY;
        }
        if (teardown === this) {
            return this;
        }
        let subscription = teardown;
        switch (typeof teardown) {
            case 'function':
                subscription = new Subscription(teardown);
            case 'object':
                if (subscription.closed || typeof subscription.unsubscribe !== 'function') {
                    return subscription;
                }
                else if (this.closed) {
                    subscription.unsubscribe();
                    return subscription;
                }
                else if (typeof subscription._addParent !== 'function' /* quack quack */) {
                    const tmp = subscription;
                    subscription = new Subscription();
                    subscription._subscriptions = [tmp];
                }
                break;
            default:
                throw new Error('unrecognized teardown ' + teardown + ' added to Subscription.');
        }
        const subscriptions = this._subscriptions || (this._subscriptions = []);
        subscriptions.push(subscription);
        subscription._addParent(this);
        return subscription;
    }
    /**
     * Removes a Subscription from the internal list of subscriptions that will
     * unsubscribe during the unsubscribe process of this Subscription.
     * @param {Subscription} subscription The subscription to remove.
     * @return {void}
     */
    remove(subscription) {
        const subscriptions = this._subscriptions;
        if (subscriptions) {
            const subscriptionIndex = subscriptions.indexOf(subscription);
            if (subscriptionIndex !== -1) {
                subscriptions.splice(subscriptionIndex, 1);
            }
        }
    }
    _addParent(parent) {
        let { _parent, _parents } = this;
        if (!_parent || _parent === parent) {
            // If we don't have a parent, or the new parent is the same as the
            // current parent, then set this._parent to the new parent.
            this._parent = parent;
        }
        else if (!_parents) {
            // If there's already one parent, but not multiple, allocate an Array to
            // store the rest of the parent Subscriptions.
            this._parents = [parent];
        }
        else if (_parents.indexOf(parent) === -1) {
            // Only add the new parent to the _parents list if it's not already there.
            _parents.push(parent);
        }
    }
}
Subscription.EMPTY = (function (empty) {
    empty.closed = true;
    return empty;
}(new Subscription()));
function flattenUnsubscriptionErrors(errors) {
    return errors.reduce((errs, err) => errs.concat((err instanceof UnsubscriptionError) ? err.errors : err), []);
}
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