HomeWork/react2/node_modules/react-redux/es/hooks/useSelector.js

import { useReducer, useRef, useMemo, useContext, useDebugValue } from 'react';
import { useReduxContext as useDefaultReduxContext } from './useReduxContext';
import { createSubscription } from '../utils/Subscription';
import { useIsomorphicLayoutEffect } from '../utils/useIsomorphicLayoutEffect';
import { ReactReduxContext } from '../components/Context';

var refEquality = function refEquality(a, b) {
  return a === b;
};

function useSelectorWithStoreAndSubscription(selector, equalityFn, store, contextSub) {
  var _useReducer = useReducer(function (s) {
    return s + 1;
  }, 0),
      forceRender = _useReducer[1];

  var subscription = useMemo(function () {
    return createSubscription(store, contextSub);
  }, [store, contextSub]);
  var latestSubscriptionCallbackError = useRef();
  var latestSelector = useRef();
  var latestStoreState = useRef();
  var latestSelectedState = useRef();
  var storeState = store.getState();
  var selectedState;

  try {
    if (selector !== latestSelector.current || storeState !== latestStoreState.current || latestSubscriptionCallbackError.current) {
      var newSelectedState = selector(storeState); // ensure latest selected state is reused so that a custom equality function can result in identical references

      if (latestSelectedState.current === undefined || !equalityFn(newSelectedState, latestSelectedState.current)) {
        selectedState = newSelectedState;
      } else {
        selectedState = latestSelectedState.current;
      }
    } else {
      selectedState = latestSelectedState.current;
    }
  } catch (err) {
    if (latestSubscriptionCallbackError.current) {
      err.message += "\nThe error may be correlated with this previous error:\n" + latestSubscriptionCallbackError.current.stack + "\n\n";
    }

    throw err;
  }

  useIsomorphicLayoutEffect(function () {
    latestSelector.current = selector;
    latestStoreState.current = storeState;
    latestSelectedState.current = selectedState;
    latestSubscriptionCallbackError.current = undefined;
  });
  useIsomorphicLayoutEffect(function () {
    function checkForUpdates() {
      try {
        var newStoreState = store.getState(); // Avoid calling selector multiple times if the store's state has not changed

        if (newStoreState === latestStoreState.current) {
          return;
        }

        var _newSelectedState = latestSelector.current(newStoreState);

        if (equalityFn(_newSelectedState, latestSelectedState.current)) {
          return;
        }

        latestSelectedState.current = _newSelectedState;
        latestStoreState.current = newStoreState;
      } catch (err) {
        // we ignore all errors here, since when the component
        // is re-rendered, the selectors are called again, and
        // will throw again, if neither props nor store state
        // changed
        latestSubscriptionCallbackError.current = err;
      }

      forceRender();
    }

    subscription.onStateChange = checkForUpdates;
    subscription.trySubscribe();
    checkForUpdates();
    return function () {
      return subscription.tryUnsubscribe();
    };
  }, [store, subscription]);
  return selectedState;
}
/**
 * Hook factory, which creates a `useSelector` hook bound to a given context.
 *
 * @param {React.Context} [context=ReactReduxContext] Context passed to your `<Provider>`.
 * @returns {Function} A `useSelector` hook bound to the specified context.
 */


export function createSelectorHook(context) {
  if (context === void 0) {
    context = ReactReduxContext;
  }

  var useReduxContext = context === ReactReduxContext ? useDefaultReduxContext : function () {
    return useContext(context);
  };
  return function useSelector(selector, equalityFn) {
    if (equalityFn === void 0) {
      equalityFn = refEquality;
    }

    if (process.env.NODE_ENV !== 'production') {
      if (!selector) {
        throw new Error("You must pass a selector to useSelector");
      }

      if (typeof selector !== 'function') {
        throw new Error("You must pass a function as a selector to useSelector");
      }

      if (typeof equalityFn !== 'function') {
        throw new Error("You must pass a function as an equality function to useSelector");
      }
    }

    var _useReduxContext = useReduxContext(),
        store = _useReduxContext.store,
        contextSub = _useReduxContext.subscription;

    var selectedState = useSelectorWithStoreAndSubscription(selector, equalityFn, store, contextSub);
    useDebugValue(selectedState);
    return selectedState;
  };
}
/**
 * A hook to access the redux store's state. This hook takes a selector function
 * as an argument. The selector is called with the store state.
 *
 * This hook takes an optional equality comparison function as the second parameter
 * that allows you to customize the way the selected state is compared to determine
 * whether the component needs to be re-rendered.
 *
 * @param {Function} selector the selector function
 * @param {Function=} equalityFn the function that will be used to determine equality
 *
 * @returns {any} the selected state
 *
 * @example
 *
 * import React from 'react'
 * import { useSelector } from 'react-redux'
 *
 * export const CounterComponent = () => {
 *   const counter = useSelector(state => state.counter)
 *   return <div>{counter}</div>
 * }
 */

export var useSelector = /*#__PURE__*/createSelectorHook();