convex/dist/esm/react/use_subscription.js

Client for the Convex Cloud

"use strict";
import { useEffect, useState } from "react";
export function useSubscription({
  // (Synchronously) returns the current value of our subscription.
  getCurrentValue,
  // This function is passed an event handler to attach to the subscription.
  // It should return an unsubscribe function that removes the handler.
  subscribe
}) {
  const [state, setState] = useState(() => ({
    getCurrentValue,
    subscribe,
    value: getCurrentValue()
  }));
  let valueToReturn = state.value;
  if (state.getCurrentValue !== getCurrentValue || state.subscribe !== subscribe) {
    valueToReturn = getCurrentValue();
    setState({
      getCurrentValue,
      subscribe,
      value: valueToReturn
    });
  }
  useEffect(() => {
    let didUnsubscribe = false;
    const checkForUpdates = () => {
      if (didUnsubscribe) {
        return;
      }
      setState((prevState) => {
        if (prevState.getCurrentValue !== getCurrentValue || prevState.subscribe !== subscribe) {
          return prevState;
        }
        const value = getCurrentValue();
        if (prevState.value === value) {
          return prevState;
        }
        return { ...prevState, value };
      });
    };
    const unsubscribe = subscribe(checkForUpdates);
    checkForUpdates();
    return () => {
      didUnsubscribe = true;
      unsubscribe();
    };
  }, [getCurrentValue, subscribe]);
  return valueToReturn;
}
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