当渲染函数React Redux中未使用该属性时，防止组件重新渲染

Question

我正在努力重新渲染一个组件。我正在使用Redux管理状态。在一个组件中，我正在组件（类）的某些方法中使用mapStateToProps从状态使用属性（（isPlaying：bool）] >>）[[render函数除外，并且我使用一些动作创建者来分配isPlaying的更改。顺便说一句，我正在使用connect（react-redux）在另一个子组件（Music Player）中使用isPlaying。这是我所期望的：更改isPlaying时，父组件不会重新渲染，并且Music Bar将重新渲染，并且我继续使用isPlaying在我的父组件的方法中。出了什么问题：即使我未在render方法中使用isPlaying，父组件也会重新渲染。抱歉，如果我在阅读时确实使您感到困惑，我不是英语母语人士。预先感谢。编辑：添加代码的简化版本。我的初始状态：

export default {
// Some Irrelevant Properties
...

playlist: {
    isPlaying: false,
    playingTrack: null,
    nextTrack: null,
    prevTrack: null,
    views: null,
    totalListens: null,
    tracks: []
}

};

这是我的父组件。 （App.js）

import ...
class App extends React.Component {
constructor(props) {
        super(props)
        this.state = {
            widgets: [],
            links: [],
            clickedTrack: null
        }

        this.musicBarRef = React.createRef()
        this._isMounted = false;

        // Binding this to the methods used in this Component
        ...

    }
    // All my methods here
    // Example of one function 
    playTrack() {
        let {isPlaying} = this.props
        if (isPlaying) {
            // Pause
        } else {
            // Play
        }
    }

    render() {
        <>
            // Some irrelevant components (don't use isPlaying)
            <TracksPlaylist tracks={this.props.tracks} and some the methods created above />
            <MusicBar ref={this.musicBarRef} and some methods created above />

            // Example of one irrelevant component that re-renders
            <Footer />
        </>
    }
}

const mapStateToProps = (state) => {
    return {
        isPlaying: state.playlist.isPlaying,
        selectedTrack: state.playlist.playingTrack,
        nextTrack: state.playlist.nextTrack,
        prevTrack: state.playlist.prevTrack,
        tracks: state.playlist.tracks,
    }
}

const mapDispatchToProps = {
    setPlaying: startPlaying, // Set isPlaying: true
    setNotPlaying: stopPlaying, // Set isPlaying: false
    // Some Irrelevent Action Creators
    ...
}

export default connect(mapStateToProps, mapDispatchToProps)(App)

这是我的减速器

import * as types from "../actions/actionTypes";
import initialState from "./initialState";

export default function musicPlayerReducer(state = initialState.playlist, action) {
    switch (action.type) {
        // Some irrelevant cases
        ...

        case types.STOP_PLAYING:
            return {...state, isPlaying: false}
        case types.START_PLAYING:
            return {...state, isPlaying: true}
        case types.NEXT_TRACK_FOUND:
            return {...state, nextTrack: action.track}
        case types.PREV_TRACK_FOUND:
            return {...state, prevTrack: action.track}
        case types.CURRENT_TRACK_FOUND:
            return {...state, playingTrack: action.track}
        default:
            return state
    }
}

App.js中提到的TracksPlaylist

import ...

class TracksPlaylist extends React.Component {

    constructor(props) {
        super(props)
    }

    render() {
        let {tracks, onPlayClick ... and other methods from App.js} = this.props
        return (
            <div className="songs">
                {
                    Object.values(tracks).length > 0 ?
                        Object.values(tracks).map((item, index) => {
                            return <Track onPlayClick={onPlayClick} key={index} item={item} />
                        }) :
                        ''
                }
            </div>
        )
    }
}
const mapStateToProps = (state) => {
    return {
        tracks: state.playlist.tracks,
    }
}

const mapDispatchToProps = {
    setPlaying: startPlaying,
    setNotPlaying: stopPlaying,

    // Some irrelevant functions
    ...
}

export default connect(mapStateToProps, mapDispatchToProps)(Tracks)

跟踪组件

import ...

class Track extends React.Component {
    constructor(props) {
        super(props)
    }

    hasInteraction(interactionType, trackId) {
        return false
    }


    render() {
        let {onPlayClick, item} = this.props
        return (
            <div key={item.track_id} className="track" id={item.track_id} data-category={item.category_name}>
                    // A lot of irrelevant JSX :)
                    <TrackAction onPlayClick={onPlayClick} item={item} />
                </div>
            </div>
        )
    }

}

export default Track

这里是TrackAction（它使用isPlaying）：

import ...

function TrackAction({item, isPlaying, playingTrack, onPlayClick}) {
    return (
        <div className="status action play-track" onClick={onPlayClick}>
            <i id={item.track_id} className={isPlaying && playingTrack.track_id === item.track_id ? 'fas fa-pause' : 'fas fa-play'} />
        </div>
    )
}

const mapStateToProps = (state) => {
    return {
        isPlaying: state.playlist.isPlaying,
        playingTrack: state.playlist.playingTrack
    }
}

export default connect(mapStateToProps)(TrackAction)

我确实使用TrackAction来重新渲染该组件，因为isPlaying发生了变化，并且已将其注册到该组件并在其render（）中使用。再次感谢。

我正在努力重新渲染一个组件。我正在使用Redux管理状态。在一个组件中，我正在通过mapStateToProps在我的状态中使用属性（isPlaying：bool）...

Answer 1

尽管您没有在isPlaying方法中使用render，但由于mapStateToProps绑定，您仍在订阅更改。