React DOM不重新渲染

Question

My React JS file is below:

The logic behind this:

1.) CreateTable renders CreateColumns , CreateRows , & ChangeResults

On the first render, CreateRows is empty, but once the component mounts, a fetch() call is made to update the rows, page re-renders and I have my table

2.) ChangeResults component is loaded which creates an input box. State for num_of_rows to an empty string (placeholder, not sure if I even need to do this).

When I input some number into the input field and hit click, onClick runs updatePage , which calls the function updateRows (in CreateTable ), that then changes the state of people_per_page . I have the console.log() to verify that this is actually happening, and it prints out as expected.

I thought that since CreateRows inherits people_per_page , and I'm changing the state of people_per_page , it would cause a re-render...but nothing is happening.

Can anyone see why that might be?

var CreateTable = React.createClass({
    getInitialState: function(){
        console.log('initial state loaded')
        return {
            'table_columns' : ['id','email', 'first', 'last', 'title', 'company', 'linkedin', 'role'],
            people_per_page: 34
        }
    },

    updateRows: function(rows) {
        console.log(rows)
        this.setState(
            {people_per_page: rows},
            function() {
                console.log(this.state.people_per_page)
            }
        )
    },

    render: function(){
        return (
            <div>
                <ChangeResults updateRows = {this.updateRows} />
                <table>
                    <CreateColumns columns={this.state.table_columns} />
                    <CreateRows num_of_rows = {this.state.people_per_page} />
                </table>
            </div>
        )   
    }
});

var ChangeResults = React.createClass({
    getInitialState: function(){
        return {
            num_of_rows : ''   
        }

    },

    handleChange: function(e) {
        this.setState({
            'num_of_rows' : e.target.value
        });
    },

    updatePage: function(){
        this.props.updateRows(this.state.num_of_rows);
    },

    render: function(){
        return (
            <div>
                Number of people per page: <br />
                <input type="text" onChange = {this.handleChange} />
                <button onClick={this.updatePage}> Update Page </button>
            </div> 
        )
    }

})

var CreateColumns = React.createClass({
    render: function(){
        var columns = this.props.columns.map(function(column, i){
            return (
                <th key={i}> 
                    {column} 
                </th>
            )
        });

        return (
            <thead>
                <tr>
                    {columns}
                </tr>
            </thead>
        )
    }
});

var CreateRows = React.createClass({
    getInitialState: function() {
        return {
            'people':[],
        }
    },

    componentDidMount: function(){
        console.log('componentDidMount running')
        this.createRow();
    },

    createRow : function(){
        console.log('starting fetch')
        fetch('http://localhost:5000/search', {
            method: 'POST',
            body: JSON.stringify({
                people_per_page: this.props.num_of_rows
            })
        })
            .then(function(response) {
                return response.json()
            })
            .then((responseJson) => {
                return this.setState({'people' : responseJson.people }) 
            });
    },


    render: function(){
        var rows = this.state.people.map(function(row, i){
            return (
                <tr key={i}>        
                    <td>{row['id']}</td>
                    <td>{row['email']}</td>
                    <td>{row['first']}</td>
                    <td>{row['last']}</td>
                    <td>{row['title']}</td>
                    <td>{row['company']}</td>
                    <td>{row['linkedin_url']}</td>
                    <td>{row['role']}</td>
                </tr>
            )
        })
        return (
            <tbody>
                {rows}
            </tbody>
        )
    }
});


ReactDOM.render(<CreateTable />, document.getElementById('content'));

Answer 1

In <CreateRows /> , componentDidMount is only called for the first render, when the component is 'mounted' on the page. After that, you need to fetch new data in componentDidUpdate or somewhere else in the application.