127 lines
2.6 KiB
JavaScript
127 lines
2.6 KiB
JavaScript
import { getBatch } from './batch'; // encapsulates the subscription logic for connecting a component to the redux store, as
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// well as nesting subscriptions of descendant components, so that we can ensure the
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// ancestor components re-render before descendants
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function createListenerCollection() {
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const batch = getBatch();
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let first = null;
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let last = null;
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return {
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clear() {
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first = null;
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last = null;
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},
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notify() {
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batch(() => {
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let listener = first;
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while (listener) {
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listener.callback();
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listener = listener.next;
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}
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});
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},
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get() {
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let listeners = [];
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let listener = first;
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while (listener) {
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listeners.push(listener);
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listener = listener.next;
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}
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return listeners;
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},
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subscribe(callback) {
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let isSubscribed = true;
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let listener = last = {
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callback,
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next: null,
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prev: last
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};
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if (listener.prev) {
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listener.prev.next = listener;
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} else {
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first = listener;
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}
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return function unsubscribe() {
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if (!isSubscribed || first === null) return;
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isSubscribed = false;
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if (listener.next) {
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listener.next.prev = listener.prev;
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} else {
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last = listener.prev;
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}
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if (listener.prev) {
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listener.prev.next = listener.next;
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} else {
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first = listener.next;
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}
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};
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}
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};
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}
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const nullListeners = {
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notify() {},
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get: () => []
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};
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export function createSubscription(store, parentSub) {
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let unsubscribe;
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let listeners = nullListeners;
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function addNestedSub(listener) {
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trySubscribe();
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return listeners.subscribe(listener);
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}
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function notifyNestedSubs() {
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listeners.notify();
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}
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function handleChangeWrapper() {
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if (subscription.onStateChange) {
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subscription.onStateChange();
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}
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}
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function isSubscribed() {
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return Boolean(unsubscribe);
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}
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function trySubscribe() {
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if (!unsubscribe) {
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unsubscribe = parentSub ? parentSub.addNestedSub(handleChangeWrapper) : store.subscribe(handleChangeWrapper);
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listeners = createListenerCollection();
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}
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}
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function tryUnsubscribe() {
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if (unsubscribe) {
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unsubscribe();
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unsubscribe = undefined;
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listeners.clear();
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listeners = nullListeners;
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}
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}
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const subscription = {
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addNestedSub,
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notifyNestedSubs,
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handleChangeWrapper,
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isSubscribed,
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trySubscribe,
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tryUnsubscribe,
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getListeners: () => listeners
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};
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return subscription;
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} |