mobx-react-lite/es/useObserver.js

Lightweight React bindings for MobX based on React 16.8+ and Hooks

var __read = (this && this.__read) || function (o, n) {
    var m = typeof Symbol === "function" && o[Symbol.iterator];
    if (!m) return o;
    var i = m.call(o), r, ar = [], e;
    try {
        while ((n === void 0 || n-- > 0) && !(r = i.next()).done) ar.push(r.value);
    }
    catch (error) { e = { error: error }; }
    finally {
        try {
            if (r && !r.done && (m = i["return"])) m.call(i);
        }
        finally { if (e) throw e.error; }
    }
    return ar;
};
import { Reaction } from "mobx";
import React from "react";
import { printDebugValue } from "./utils/printDebugValue";
import { addReactionToTrack, recordReactionAsCommitted } from "./utils/reactionCleanupTracking";
import { isUsingStaticRendering } from "./staticRendering";
function observerComponentNameFor(baseComponentName) {
    return "observer".concat(baseComponentName);
}
/**
 * We use class to make it easier to detect in heap snapshots by name
 */
var ObjectToBeRetainedByReact = /** @class */ (function () {
    function ObjectToBeRetainedByReact() {
    }
    return ObjectToBeRetainedByReact;
}());
function objectToBeRetainedByReactFactory() {
    return new ObjectToBeRetainedByReact();
}
export function useObserver(fn, baseComponentName) {
    if (baseComponentName === void 0) { baseComponentName = "observed"; }
    if (isUsingStaticRendering()) {
        return fn();
    }
    var _a = __read(React.useState(objectToBeRetainedByReactFactory), 1), objectRetainedByReact = _a[0];
    // Force update, see #2982
    var _b = __read(React.useState(), 2), setState = _b[1];
    var forceUpdate = function () { return setState([]); };
    // StrictMode/ConcurrentMode/Suspense may mean that our component is
    // rendered and abandoned multiple times, so we need to track leaked
    // Reactions.
    var reactionTrackingRef = React.useRef(null);
    if (!reactionTrackingRef.current) {
        // First render for this component (or first time since a previous
        // reaction from an abandoned render was disposed).
        var newReaction = new Reaction(observerComponentNameFor(baseComponentName), function () {
            // Observable has changed, meaning we want to re-render
            // BUT if we're a component that hasn't yet got to the useEffect()
            // stage, we might be a component that _started_ to render, but
            // got dropped, and we don't want to make state changes then.
            // (It triggers warnings in StrictMode, for a start.)
            if (trackingData_1.mounted) {
                // We have reached useEffect(), so we're mounted, and can trigger an update
                forceUpdate();
            }
            else {
                // We haven't yet reached useEffect(), so we'll need to trigger a re-render
                // when (and if) useEffect() arrives.
                trackingData_1.changedBeforeMount = true;
            }
        });
        var trackingData_1 = addReactionToTrack(reactionTrackingRef, newReaction, objectRetainedByReact);
    }
    var reaction = reactionTrackingRef.current.reaction;
    React.useDebugValue(reaction, printDebugValue);
    React.useEffect(function () {
        // Called on first mount only
        recordReactionAsCommitted(reactionTrackingRef);
        if (reactionTrackingRef.current) {
            // Great. We've already got our reaction from our render;
            // all we need to do is to record that it's now mounted,
            // to allow future observable changes to trigger re-renders
            reactionTrackingRef.current.mounted = true;
            // Got a change before first mount, force an update
            if (reactionTrackingRef.current.changedBeforeMount) {
                reactionTrackingRef.current.changedBeforeMount = false;
                forceUpdate();
            }
        }
        else {
            // The reaction we set up in our render has been disposed.
            // This can be due to bad timings of renderings, e.g. our
            // component was paused for a _very_ long time, and our
            // reaction got cleaned up
            // Re-create the reaction
            reactionTrackingRef.current = {
                reaction: new Reaction(observerComponentNameFor(baseComponentName), function () {
                    // We've definitely already been mounted at this point
                    forceUpdate();
                }),
                mounted: true,
                changedBeforeMount: false,
                cleanAt: Infinity
            };
            forceUpdate();
        }
        return function () {
            reactionTrackingRef.current.reaction.dispose();
            reactionTrackingRef.current = null;
        };
    }, []);
    // render the original component, but have the
    // reaction track the observables, so that rendering
    // can be invalidated (see above) once a dependency changes
    var rendering;
    var exception;
    reaction.track(function () {
        try {
            rendering = fn();
        }
        catch (e) {
            exception = e;
        }
    });
    if (exception) {
        throw exception; // re-throw any exceptions caught during rendering
    }
    return rendering;
}
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