Question

我尝试使用ReactJS更新状态时看到以下错误，尽管已经绑定了该函数。代码如下所示。方法绑定，console.log显示api正在返回正确的数据。

潜在的未处理拒绝[1] TypeError：无法读取属性＆＃39; setState＆＃39; of undefined`

import React from 'react';
import {BootstrapTable, TableHeaderColumn} from 'react-bootstrap-table';

var rest, mime, client;

rest = require('rest');
mime = require('rest/interceptor/mime');

import ParameterDialog from './parameter-dialog';

const categoryAvailable = {
    'POS': 'POS'
};

const options = {
    noDataText: 'No parameters founds.'
}

function enumFormatter(cell, row, enumObject) {
    return enumObject[cell];
}

export default class ParameterContainer extends React.Component {

    constructor(props) {
        super(props);
        this.state = { parameters: [] };
        this.client = rest.wrap(mime);
        this.fetchFromApi = this.fetchFromApi.bind(this);
    }

    fetchFromApi() {
        this.client({ path: '/api/parameters' }).then(function(response) {
            console.log(response);
            console.log(response.entity);
            this.setState( {parameters: response.entity} );
        });
    }

    componentDidMount() {
        this.fetchFromApi();
    }

    render() {
        return (
            <div>
                <h2>Parameters</h2>
                <ParameterDialog />
                <BootstrapTable data={this.state.parameters} options={options} pagination>
                    <TableHeaderColumn isKey dataField='id'>ID</TableHeaderColumn>
                    <TableHeaderColumn dataField='category' filterFormatted dataFormat={enumFormatter} formatExtraData={categoryAvailable}
                        filter={{type: 'SelectFilter', options: categoryAvailable}}>Category</TableHeaderColumn>
                    <TableHeaderColumn dataField='subCategory'>Sub Category</TableHeaderColumn>
                    <TableHeaderColumn dataField='parameter' filter={ { type: 'TextFilter', delay: 500 } }>Parameter</TableHeaderColumn>
                    <TableHeaderColumn dataField='type' filterFormatted dataFormat={enumFormatter} formatExtraData={this.props.parentState.parameterTypes}
                                       filter={{type: 'SelectFilter', options: this.props.parentState.parameterTypes}}>Type</TableHeaderColumn>
                    <TableHeaderColumn dataField='roles'>Roles</TableHeaderColumn>
                </BootstrapTable>
            </div>
        )
    }
}

Answer 1

你的内部函数.then也必须绑定

您可以使用（）=＆gt;句法

    fetchFromApi() {
        this.client({ path: '/api/parameters' }).then(response => {
            console.log(response);
            console.log(response.entity);
            this.setState( {parameters: response.entity} );
        });
    }

或只是绑定函数

    fetchFromApi() {
        this.client({ path: '/api/parameters' }).then((function(response) {
            console.log(response);
            console.log(response.entity);
            this.setState( {parameters: response.entity} );
        }).bind(this);
    }

Answer 2

看起来在promise.then的上下文中调用了setState，而不是类。快速补救措施是将其更改为箭头函数，如：

.then(response => {
    console.log(response);
    console.log(response.entity);
    this.setState( {parameters: response.entity} );
});

可能未处理的拒绝[1] TypeError：无法读取属性＆＃39; setState＆＃39;未定义的

2 个答案: