Question

我将一个对象作为道具传递给了我的组件。我可以访问它，并将它作为一个对象返回，但是当我尝试访问该对象之外的某个项目（我确定它存在）时，它说未定义。

运行此命令时：

import React, { Component } from 'react';
import { Text } from 'react-native';
import { CardSection } from './common';

class ListItem extends Component {
    render() {
        const { titleStyle } = styles;
        console.log(this.props.library);
        console.log(this.props.library.title);

        return (
            <CardSection>
                <Text style={titleStyle}>{this.props.library.title}</Text>
            </CardSection>
        );
    }
}

我明白了：

{…}

    index: 0

    item: Object { id: 0, title: "Webpack", description: "Webpack is a module bundler. It packs CommonJs/AMD modules i. e. for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand." }

undefined

最后console.log()的结果在底部。

这是我传递库对象的组件：

import React, { Component } from 'react';
import { FlatList } from 'react-native';
import { connect } from 'react-redux';
import ListItem from './ListItem';

class LibraryList extends Component {
   renderItem(library) {
        return <ListItem library={library} />;
    }

    render() {
        return (
            <FlatList
            data={this.props.libraries}
            renderItem={this.renderItem}
            keyExtractor={library => library.id.toString()}
            />
        );
    }
}

const mapStateToProps = (state) => ({ libraries: state.libraries });

export default connect(mapStateToProps)(LibraryList);

在此处查看完整代码：https://github.com/ceerees12/tech_stack

Answer 1

您没有在组件中传递title，如果您在title组件中传递了道具ListItem，那么您将能够访问this.props.title，并且如果title处于library属性中，则应该this.props.library.title。

Answer 2

尝试将import random import pandas as pd import numpy as np from matplotlib import pyplot as plt p = [.1,.2,.3,.4,.5,.6,.7, .8,.9] p = [random.choice(p) for _ in range(180)] r = np.linspace(.001, .999, num=180) df = pd.DataFrame({'pct':p, 'ratio':r}) df1 = df.groupby('pct')['ratio'].mean() df1.plot() plt.show() plt.close()更改为renderItem={this.renderItem}

对象内的项目返回为未定义

2 个答案: