Asked  7 Months ago    Answers:  5   Viewed   56 times

I just got started with ReactJS and am a little stuck on a problem that I have.

My application is essentially a list with filters and a button to change the layout. At the moment I'm using three components: <list />, < Filters /> and <TopBar />, now obviously when I change settings in < Filters /> I want to trigger some method in <list /> to update my view.

How can I make those 3 components interact with each other, or do I need some sort of global data model where I can just make changes to?

 Answers

24

The best approach would depend on how you plan to arrange those components. A few example scenarios that come to mind right now:

  1. <Filters /> is a child component of <List />
  2. Both <Filters /> and <List /> are children of a parent component
  3. <Filters /> and <List /> live in separate root components entirely.

There may be other scenarios that I'm not thinking of. If yours doesn't fit within these, then let me know. Here are some very rough examples of how I've been handling the first two scenarios:

Scenario #1

You could pass a handler from <List /> to <Filters />, which could then be called on the onChange event to filter the list with the current value.

JSFiddle for #1 ?

/** @jsx React.DOM */

var Filters = React.createClass({
  handleFilterChange: function() {
    var value = this.refs.filterInput.getDOMNode().value;
    this.props.updateFilter(value);
  },
  render: function() {
    return <input type="text" ref="filterInput" onChange={this.handleFilterChange} placeholder="Filter" />;
  }
});

var List = React.createClass({
  getInitialState: function() {
    return {
      listItems: ['Chicago', 'New York', 'Tokyo', 'London', 'San Francisco', 'Amsterdam', 'Hong Kong'],
      nameFilter: ''
    };
  },
  handleFilterUpdate: function(filterValue) {
    this.setState({
      nameFilter: filterValue
    });
  },
  render: function() {
    var displayedItems = this.state.listItems.filter(function(item) {
      var match = item.toLowerCase().indexOf(this.state.nameFilter.toLowerCase());
      return (match !== -1);
    }.bind(this));

    var content;
    if (displayedItems.length > 0) {
      var items = displayedItems.map(function(item) {
        return <li>{item}</li>;
      });
      content = <ul>{items}</ul>
    } else {
      content = <p>No items matching this filter</p>;
    }

    return (
      <div>
        <Filters updateFilter={this.handleFilterUpdate} />
        <h4>Results</h4>
        {content}
      </div>
    );
  }
});

React.renderComponent(<List />, document.body);

Scenario #2

Similar to scenario #1, but the parent component will be the one passing down the handler function to <Filters />, and will pass the filtered list to <List />. I like this method better since it decouples the <List /> from the <Filters />.

JSFiddle for #2 ?

/** @jsx React.DOM */

var Filters = React.createClass({
  handleFilterChange: function() {
    var value = this.refs.filterInput.getDOMNode().value;
    this.props.updateFilter(value);
  },
  render: function() {
    return <input type="text" ref="filterInput" onChange={this.handleFilterChange} placeholder="Filter" />;
  }
});

var List = React.createClass({
  render: function() {
    var content;
    if (this.props.items.length > 0) {
      var items = this.props.items.map(function(item) {
        return <li>{item}</li>;
      });
      content = <ul>{items}</ul>
    } else {
      content = <p>No items matching this filter</p>;
    }
    return (
      <div className="results">
        <h4>Results</h4>
        {content}
      </div>
    );
  }
});

var ListContainer = React.createClass({
  getInitialState: function() {
    return {
      listItems: ['Chicago', 'New York', 'Tokyo', 'London', 'San Francisco', 'Amsterdam', 'Hong Kong'],
      nameFilter: ''
    };
  },
  handleFilterUpdate: function(filterValue) {
    this.setState({
      nameFilter: filterValue
    });
  },
  render: function() {
    var displayedItems = this.state.listItems.filter(function(item) {
      var match = item.toLowerCase().indexOf(this.state.nameFilter.toLowerCase());
      return (match !== -1);
    }.bind(this));

    return (
      <div>
        <Filters updateFilter={this.handleFilterUpdate} />
        <List items={displayedItems} />
      </div>
    );
  }
});

React.renderComponent(<ListContainer />, document.body);

Scenario #3

When the components can't communicate between any sort of parent-child relationship, the documentation recommends setting up a global event system.

Tuesday, June 1, 2021
 
dirigibleplum
answered 7 Months ago
14

In JSX, lower-case tag names are considered to be HTML tags. However, lower-case tag names with a dot (property accessor) aren't.

See HTML tags vs React Components.

  • <component /> compiles to React.createElement('component') (html tag)
  • <Component /> compiles to React.createElement(Component)
  • <obj.component /> compiles to React.createElement(obj.component)
Tuesday, June 1, 2021
 
ranhan
answered 7 Months ago
78

You are missing binding in your constructor, also you don't need to pass props if you are not using them in the constructor. Also you need to import { PropTypes } from 'react'

class SearchBar extends React.Component {

  constructor() {
    super();
    this.handler = this.handler.bind(this);
  }

  handler(e){
    this.props.filterUser(e.target.value);
  }

  render () {
    return (
      <div>
        <input type='text' className='from-control search-bar' placeholder='Search' onChange={this.handler} />
      </div>
    );
  }
}


export default class User extends React.Component {
  constructor() {
    super();
    this.filterUser = this.filterUser.bind(this);
    this.state = { name: '', age: '', filter: '' };
  } 

  filterUser(filterValue){
    this.setState({
      filter: filterValue
    });
  }

  render() {
    return ( 
      <div>
        <SearchBar filterUser={this.filterUser} />
        <span>Value: {this.state.filter}</span>
      </div>
    );
  }
}
Thursday, June 17, 2021
 
tadman
answered 6 Months ago
76

I figured it out - the tutorial is missing two things:

  1. The script inclusion should be done thus, with a type declaration:

    <script type="text/jsx" src="/Scripts/Tutorial.jsx"></script>

  2. The JSX transformer needs to be included:

    <script src="http://fb.me/JSXTransformer-0.12.2.js"></script>

So the full HTML output by the Razor view should look like this:

<!DOCTYPE html>
<html>
  <head>
    <title>Hello React</title>
  </head>
  <body>
    <div id="content"></div>
    <script src="http://fb.me/react-0.12.2.js"></script>
    <script src="http://fb.me/JSXTransformer-0.12.2.js"></script>
    <script type="text/jsx" src="/Scripts/Tutorial.jsx"></script>
  </body>
</html>

Looks like they need to update their tutorial.

Update:

Commenter @DanielLoNigro added this helpful tip:

Actually if you're using ReactJS.NET, you don't need to use the client-side JSXTransformer. Just ensure that the JSX handler is configured in your Web.config file (there should be a handler for .jsx).

Monday, August 16, 2021
 
Robert C. Barth
answered 4 Months ago
16

The solution is to pass a mocked function directly to the sub components and test them. Anything involving more than one "sub-component" is usually not truly a unit test as you are testing multiple units of functionality.

So I would create MemberList-test.js:

describe('MemberList', function () {
  it('calls the add handler when add is clicked', function () {
    var Component = TestUtils.renderIntoDocument(
      <MemberList add={ jest.genMockFn() } />
      );

    const btn = TestUtils.findRenderedDOMComponentWithTag(Component, 'span')

    TestUtils.Simulate.change(btn);

    expect(Component.add.mock.calls.length).toBe(1)

  })
})

Then rather than trying to test your member component directly within the same test your should create Member-test.js:

describe('Member', function () {
  it('calls the add handler when add is clicked', function () {
    var Component = TestUtils.renderIntoDocument(
      <Member remove={ jest.genMockFn() } />
      );

    const btn = TestUtils.findRenderedDOMComponentWithTag(Component,
      'HOWEVER YOU FIND YOUR REMOVE BUTTON')

    TestUtils.Simulate.change(btn);

    expect(Component.remove.mock.calls.length).toBe(1)

  })
})

Now the assertion your are missing is that the remove handler that is passed into the member list is correctly getting passed down to the Member component. So let's add another test to the MemberList-test.js

it('passes correct information to the children', function () {
  var MemberMock = require('../Member')
  var removeFn = jest.genMockFn();

  var testMember = {WHATEVER YOUR MEMBER OBJECT LOOKS LIKE}

  var Component = TestUtils.renderIntoDocument(
    <MemberList members={ [testMember] }
      remove={ removeFn } />
    );

  // We expect the member component to be instantiated 1 time and
  // passed the remove function we defined
  // as well as a key and the data
  expect(MemberMock.mock.calls).toEqual([[{key: 0, data: testMember,
    remove: removeFn}]])

})

Then you simply do the same pattern with the form component. Mocking the member list and the button and testing them separately and seeing that the correct handlers and data are passed down.

Hopefully this makes sense and if not just reply and maybe I can walk you through it on Skype or something.

Sunday, October 17, 2021
 
Mark Ransom
answered 2 Months ago
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