Namespaced components

"Shawn, you must have used modules and packages in languages such as Ruby and Java. The idea behind these concepts is to create a namespace hierarchy of code such that the code from one module or package doesn't interfere with another."

"Yes. Is something like this available with React?" Shawn asked.

"Yes. React allows creating components that are namespaced under a parent component so that they don't interfere with other components or global functions."

"We are using very generic names such as Rows and Headings that can be used later in other parts of the app too. So it makes sense to namespace them now, rather than later." explained Mike.

"Agreed. Let's do it right away," Shawn.

"We need to represent the top-level component as custom component rather than using the <table> element."

var RecentChangesTable = React.createClass({
  render: function() {
    return <table>
             {this.props.children}
           </table>;
  } 
});

"Now, we can replace the App component to use RecentChangesTable instead of <table>."

var App = React.createClass({
  render: function(){
    return(<RecentChangesTable>
                <Headings headings = {this.props.headings} />
                <Rows changeSets = {this.props.changeSets} />
           </RecentChangesTable>);
    }
});

"Hang on, Mike. We just replaced <table> with a custom component. All it does is just render this.props.children. How does it get all the headings and rows?" Shawn asked.

"Ah! Nice observation. React, by default, captures all the child nodes between open and close tags of a component in an array and adds it to the props of that component as this.props.children. So we can render it using {this.props.children}. We will get all Headings and Rows as this.props.children in the RecentChangesTable component. The output is the same as before, when we used the <table> tag directly."

"Awesome!" exclaimed Shawn.

"Cool. Let's move on next step by namespacing all other components under RecentChangesTable."

RecentChangesTable.Headings = React.createClass({
  render: function() {
    var headings = this.props.headings.map(function(name) {
      return(<RecentChangesTable.Heading heading = {name}/>);
    });

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

RecentChangesTable.Heading = React.createClass({
  render: function() {
    return(<th>
             {this.props.heading}
           </th>);
  }
});


RecentChangesTable.Row = React.createClass({
  render: function() {
    return(<tr>
             <td>{this.props.changeSet.when}</td>
             <td>{this.props.changeSet.who}</td>
             <td>{this.props.changeSet.description}</td>
          </tr>);
  }
});

RecentChangesTable.Rows = React.createClass({
  render: function() {
    var rows = this.props.changeSets.map(function(changeSet) {
      return(<RecentChangesTable.Row changeSet = {changeSet}/>);
    });

    return (<tbody>{rows}</tbody>);
  }
});

"We will also need to update the App component to use namespaced components now."

var App = React.createClass({
  render: function(){
    return(<RecentChangesTable>
                 <RecentChangesTable.Headings headings = {this.props.headings} />
                 <RecentChangesTable.Rows changeSets = {this.props.changeSets} />
               </RecentChangesTable>);
    }
});

"We are now done. Everything is namespaced under RecentChangesTable now", said Mike.