反应路由器：从路由器侦听事件获取参数失败

Question

我发现当尝试使用 react-router router.listen(...) 获取路由参数时失败了。通过使用 window.location.pathname.split('route/')[1]，我可以获得参数。有什么建议吗？

我一直在努力弄清楚为什么会这样。到目前为止，我注意到它在第一次路由更改（url 更改）时失败 - 我的意思是，通过使用，我的 url 从 /param/y 更改为 /param/x；但该参数仅在我再次单击时可用。我想这可能与我的行为或我的组件有关？或者监听器在反应生命周期中的位置？

不确定我是否在错误的生命周期方法中声明了事件侦听器，或者；正如我一直在想的那样，我正在将路由传递给 Store，但我认为我正在为这个事件使用 withRouter(Component)。我想我需要改用 redux 的路由状态。我想

具有侦听器的组件：

import React, { Component } from 'react';
import { connect } from 'react-redux';
import { withRouter } from 'react-router';
import { setActiveQuestion, setQuestionAnswer } from '../actions/index';
import { bindActionCreators } from 'redux';
import { Link } from 'react-router';
import Navbar from '../containers/navbar';

class Question extends Component {
    constructor(props) {
        super(props);
        this.getClassName = this.getClassName.bind(this);
    }
    componentWillMount() {
        this.setEventListeners();
    }

    setEventListeners() {
        this.props.router.listen(() => {
            // using location pathname instead, since props.params fail
            //let question_id = this.props.params.question_id;
            let question_id = window.location.pathname.split('question/')[1]
            this.props.setActiveQuestion(question_id);
        });
    }

    setAnswer(answer_id) {
        let question_id = this.props.question.id;
        this.props.setQuestionAnswer(question_id, answer_id);
    }

    getClassName(answers, item_answer_id) {

        let classes = [];

        // find the answer for the active question
        let answer_index = _.findIndex(answers, (answer) => {
            return answer.question_id === this.props.question.id;
        });

        // if there's no answer yet, skip class placement
        if (answer_index === -1) {
            return;
        }

        let answer = answers[answer_index];

        // Test cases
        const isUserCorrect = () => {
            return answer.answer_id == answer.correct_answer_id && item_answer_id == answer.correct_answer_id
        }

        const isUserAnswer = () => {
            return answer.answer_id === item_answer_id;
        }

        const isCorrectAnswer = () => {
            return item_answer_id == answer.correct_answer_id;
        }

        // Test and set the correct case classname for styling
        if (isUserCorrect()) {
            classes.push('user_correct_answer');
        }

        if (isUserAnswer()) {
            classes.push('user_answer');
        }

        if (isCorrectAnswer()) {
            classes.push('correct_answer');
        }

        return classes.length > 0 ? classes.join(' ') : '';

    }

    answersList() {
        return this.props.question.answers.map((answer) => {
            return <li className={ this.getClassName(this.props.answers, answer.id) } key={ answer.id } onClick={ () => this.setAnswer(answer.id) }>{ answer.text }</li>
        });
    }

    render() {
        return (
            <div>
                <div className='question-container'>
                    <h2>{ this.props.question && this.props.question.question }</h2>
                    <ul>
                    {
                        this.props.question &&
                        this.answersList()
                    }
                    </ul>
                </div>
                <Navbar />
            </div>
        );
    }
}

function mapStateToProps(state, ownProps) {
    return {
        question: state.questions.active,
        answers: state.answers
    }
}

function matchDispatchToProps(dispatch) {
    return bindActionCreators({
        setActiveQuestion: setActiveQuestion,
        setQuestionAnswer: setQuestionAnswer
    }, dispatch);
}

export default connect(mapStateToProps, matchDispatchToProps)(withRouter(Question));

这是减速器：

import { FETCH_QUESTIONS, SET_ACTIVE_QUESTION } from '../actions/index';
import _ from 'lodash';

const INITIAL_STATE = {
    loading: true,
    list: [],
    active: 0

};

export default function(state = INITIAL_STATE, action) {

    switch (action.type) {

        case FETCH_QUESTIONS:

            return Object.assign({}, state, {
                loading: false,
                list: action.payload
            });

        break;

        case SET_ACTIVE_QUESTION:

            // retrieve the active question by the route param `question id`
            let question_id = parseInt(action.payload);
            let question = _.find(state.list, function (question) {
                return question.id === question_id;
            });

            return Object.assign({}, state, {
                active: question
            });

        break;

        default:
            return state;

    }

};

应用入口点index.js：

import React from 'react';
import ReactDOM from "react-dom";
import { Router, browserHistory } from 'react-router';
import { syncHistoryWithStore } from 'react-router-redux'
import { createStore, applyMiddleware } from 'redux';
import { Provider } from 'react-redux';
import routes from './config/routes';
import reducers from './reducers';
import promise from 'redux-promise';

const createStoreWithMiddleware = applyMiddleware(promise)(createStore);
const store = createStoreWithMiddleware(reducers);
const history = syncHistoryWithStore(browserHistory, store);

ReactDOM.render(
    <Provider store={ store }>
        <Router history={ history } routes={ routes } />
    </Provider>,
    document.getElementById('app')
);

router.js 文件：

import { combineReducers } from 'redux';
import questionsReducer from './reducer_questions';
import answerReducer from './reducer_answers';
import { routerReducer } from 'react-router-redux'

const rootReducer = combineReducers({
    questions: questionsReducer,
    answers: answerReducer,
    routing: routerReducer
});

export default rootReducer;

Answer 1

我找到了基于@TryingToImprove 反馈的解决方案，我非常感谢。我假设我需要使用 withRouter 并将 MyComponent 包装在其中，然后监听路由器位置的变化，但这显然是错误的；原因是因为我存储了来自 Reducer 的路由参数，所以我可以在 mapStateToProps 期间随时调用它。更好的解释是查看以下代码：

function mapStateToProps(state, ownProps) {
    return {
        my_parameter_name: ownProps.params.my_parameter_name
    }
}

export default connect(mapStateToProps)(MyComponent);

原始源代码已更改，将如下所示：

import React, { Component } from 'react';
import { connect } from 'react-redux';
import { withRouter } from 'react-router';
import { setActiveQuestion, setQuestionAnswer } from '../actions/index';
import { bindActionCreators } from 'redux';
import { Link } from 'react-router';
import Navbar from '../containers/navbar';

class Question extends Component {
    constructor(props) {
        super(props);
        this.getClassName = this.getClassName.bind(this);
    }

    componentWillMount() {
        this.props.setActiveQuestion(this.props.question_id);
    }

    componentWillReceiveProps(nextProps) {
        if (this.props.question_id != nextProps.question_id) {
            this.props.setActiveQuestion(nextProps.question_id);
        }
    }

    setAnswer(answer_id) {
        let question_id = this.props.question.id;
        this.props.setQuestionAnswer(question_id, answer_id);
    }

    getClassName(answers, item_answer_id) {

        let classes = [];

        // find the answer for the active question
        let answer_index = _.findIndex(answers, (answer) => {
            return answer.question_id === this.props.question.id;
        });

        // if there's no answer yet, skip class placement
        if (answer_index === -1) {
            return;
        }

        let answer = answers[answer_index];

        // Test cases
        const isUserCorrect = () => {
            return answer.answer_id == answer.correct_answer_id && item_answer_id == answer.correct_answer_id
        }

        const isUserAnswer = () => {
            return answer.answer_id === item_answer_id;
        }

        const isCorrectAnswer = () => {
            return item_answer_id == answer.correct_answer_id;
        }

        // Test and set the correct case classname for styling
        if (isUserCorrect()) {
            classes.push('user_correct_answer');
        }

        if (isUserAnswer()) {
            classes.push('user_answer');
        }

        if (isCorrectAnswer()) {
            classes.push('correct_answer');
        }

        return classes.length > 0 ? classes.join(' ') : '';

    }

    answersList() {
        return this.props.question.answers.map((answer) => {
            return <li className={ this.getClassName(this.props.answers, answer.id) } key={ answer.id } onClick={ () => this.setAnswer(answer.id) }>{ answer.text }</li>
        });
    }

    render() {
        return (
            <div>
                <div className='question-container'>
                    <h2>{ this.props.question && this.props.question.question }</h2>
                    <ul>
                    {
                        this.props.question &&
                        this.answersList()
                    }
                    </ul>
                </div>
                <Navbar />
            </div>
        );
    }
}

function mapStateToProps(state, ownProps) {
    return {
        question_id: ownProps.params.question_id,
        question: state.questions.active,
        answers: state.answers
    }
}

function matchDispatchToProps(dispatch) {
    return bindActionCreators({
        setActiveQuestion: setActiveQuestion,
        setQuestionAnswer: setQuestionAnswer
    }, dispatch);
}

export default connect(mapStateToProps, matchDispatchToProps)(Question);

Answer 2

与其收听路由器，不如看看 withRotuer。

它将允许您访问 connect..

中的 params 对象

withRouter(connect(function(state, props) { 
    return { question_id: props.params.question_id }; 
})(MyComponent)

然后您可以收听 componentDidMount/componentWillMount 和 componentWillReceiveProps(nextProps

componentWillMount() {
    this.props.setActiveQuestion(this.props.question_id);
}

componentWillReceiveProps(nextProps) {
    if (this.props.question_id != nextProps.question_id) {
        this.props.setActiveQuestion(nextProps.question_id);
    }
}

现在你的组件不需要知道 react-router 并且更可重用，加上你当前的设置你的组件将永远不会停止监听路由变化（因为缺少“router.removeListner”）这可能导致问题。

可在此处找到解释 withRouter 的精彩视频 https://egghead.io/lessons/javascript-redux-using-withrouter-to-inject-the-params-into-connected-components?course=building-react-applications-with-idiomatic-redux

反应路由器：从路由器侦听事件获取参数失败

react-router: get param from the router listen event fails

javascript

reactjs

react-router

react-router-redux