EWD 3 Training Course Part 37: Building a React.js application with ewd-xpress Part 1

Copyright © 2016 M/Gateway Developments Ltd
EWD 3 Training Course
Part 37
Building a React.js-based
QEWD Application
(a) Getting started
Rob Tweed
Director, M/Gateway Developments Ltd
Twitter: @rtweed

Assumptions
• You understand the basic principles of
React.js
• If not, try taking this introductory course:
– https://www.udemy.com/introduction-to-reactjs
• You've installed Node.js and an
appropriate database:
– Windows or OS X: Caché or GlobalsDB
– Linux: Redis, Caché, GlobalsDB or GT.M

Setting up the React.js Environment
• Ensure that you've installed:
– QEWD
– qewd-monitor
– ewd-client
• If you haven't done so, here's how:
– cd ~/qewd // or wherever you want your QEWD environment
– npm install qewd qewd-monitor ewd-client

If you're using Linux
• You can use the QEWD / React installer:
cd ~
wget https://raw.githubusercontent.com/robtweed/qewd/master/installers/reactEnvironment.sh
source reactEnvironment.sh

Otherwise do it manually
cd ~/qewd
npm install react react-dom babelify babel-preset-react react-bootstrap
npm install react-toastr react-select socket.io-client
npm install jquery ewd-client ewd-react-tools qewd-react
npm install -g browserify
npm install -g uglify-js

Create a new application folder
cd qewdwww
mkdir react-demo1
cd react-demo1
npm install babel-preset-es2015

Ready to start developing!

index.html
~/qewd/www/react-demo1/index.html
<html xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title id="QEWD React.js Example"></title>
</head>
<body>
<div id="content"></div>
<script src="bundle.js"></script>
</body>
</html>

app.js
~/qewd/www/react-demo1/app.js
var reactLoader = require('qewd-react').loader;
var params = {
applicationName: 'react-demo1',
MainPage: require('./MainPage')
};
reactLoader(params);

MainPage.js
c:ewd3wwwreact-demo1MainPage.js
"use strict"
var React = require('react');
var MainPage = React.createClass({
render: function() {
console.log('rendering MainPage');
return (
<div>
This is my test React.js Application
</div>
);
}
});
module.exports = MainPage;

Bundle it
cd ~/qewd/www/react-demo1
browserify -t [ babelify --compact false --presets [es2015 react] ] app.js > bundle.js
You should now see bundle.js in the ~/qewd/www/react-demo1 folder

Try it

So what just happened?

It's a standard React.js App…
• But it has automated:
– EWD 3 / ewd-client startup
– QEWD application registration
• Used qewd-react.loader to do this

The startup sequence
• Explained in an earlier part of the course:
– Wait until the browser's DOM is ready
– Then invoke EWD.start()
• Passing socket.io object as an argument if using
web-sockets
– When EWD has started
• You need to wait until your QEWD application has
been registered in the QEWD back-end
– Now your application is ready for user interaction

Doing this in React is more tricky
• Must use React's life-cycle methods
– If any of these are invoked, DOM is ready
• Can therefore start EWD within them
– BUT the top-level component will still render while EWD is
starting
– SO you need two render alternatives, dependent on a state
variable's value
• 'Please wait' message; or
• Render the application's main component
– AND
• reset the state variable's value when EWD has started and
application has been registered
• pass EWD object into main component as a prop

A lot to remember
• Need to do all of these things every time you
want to start any QEWD application
– Lots to remember and potentially go wrong
– Ideal candidate for automation
• So all this behaviour is pre-written for you in the
qewd-react module
– Let it do all that startup stuff
– You just focus on the main and subsequent modules
for your application

By all means take a look
• ~/qewd/node_modules/qewd-react
– /lib/loader.js
– Uses the componentWillMount() and
componentDidMount() lifecycle methods
• EWD is started in the latter
– Uses a state variable that flips when your application
is registered
• Causing your main component to render
• It's then over to you

Hierarchy of Components
• Your QEWD application must be written as a
hierarchy of React components
– Each is a self-contained module
– Each one will need access to the EWD object
• To send messages to the QEWD back-end
• To handle responses/messages sent/returned from the
QEWD back-end
• Components are bundled for use in browser
– Using WebPack or Browserify

We saw this before
• See Part 30 of this course (Modularising QEWD
Applications)
– From around slide 55
• The EWD object must be made available to
each module
– BUT it must be the post-registration instance of the
EWD object
• So it has the send() method, etc and session token available

How's this done with React?
Let's look at the render() function in that loader module…

render: function render() {
var componentPath = ['app'];
var renderComponent;
if (this.state.status === 'wait') {
renderComponent = React.createElement(
'div',
null,
'Please wait...'
);
} else {
renderComponent = React.createElement(MainPage, {
controller: this.controller,
componentPath: componentPath
});
}
return renderComponent;
}
});

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
Here's the "Please wait"
message which appears
while EWD is starting and
application is being registered

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
Here's how it invokes
your main component
instead, once everything
has started

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
Here's how it invokes
your main component
instead, once everything
has started
Your main component
is referred to as
MainPage

Where's the EWD object?
'div',
null,
'Please wait...'
);
} else {
});
}
}
});
But where is the EWD
object?

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
This is it

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
EWD is part of
an object I've called
the controller

'div',
null,
'Please wait...'
);
} else {
});
}
}
});
EWD is part of
an object I've called
the controller
This object is
instantiated for you
and passed to your
Main module as a
prop named controller

Separation of Concerns
• An important principle of modern web
application development is separation of
concerns
– Move away from monolithic programming
– Each key aspect of an application is kept
separate
• Easier to maintain and understand
• More scalable as application grows in size

React focuses on the View
• Your React components should just
describe the View aspect of your
application
– What it looks like under various situations as
the application is used
• The other aspects of your application,
commonly referred to as the Model and
Controller, should, for best practice, be
kept separate from the View

The controller object
• Provides a place to describe the dynamic
behaviour that needs to take place in any
of your application's React components
• The controller object is passed as a prop
to any of your components that requires
dynamic behaviour

• The controller object is initially created for
you by the qewd-react loader module and
passed to your MainPage module as a
prop
– You refer to it as this.props.controller
– The controller object includes within it the
post-registration EWD object
• eg this.props.controller.send() allows you to send
messages to the QEWD back-end

• The idea is for you to extend the controller object
in each of your React components to define the
behaviour of that component:
– Events
– Messages to be sent
– Responses to be handled
– Corresponding changes to state variables within the
component
• Which cause a re-render of the component and its child
components

Passing on the controller object
• qewd-react's loader module creates the
controller object for you and passes it to
your MainPage component
• It's up to you to pass it on to any of your
other React components as a prop

So let's review the demo app

index.html
<head>
</head>
<body>
</body>
</html>
Place-holder div into which
React renders its generated
mark-up
Your application will be built
up from within this div
Always give it an id of 'content'

index.html
<head>
<title id="ewd-xpress React.js Example"></title>
</head>
<body>
</body>
</html>
Load the bundled
application's Javascript
into the browser
You'll use Browserify
or WebPack to turn your
hierarchy of React
Components into a
bundle file

app.js
var params = {
};
This is the top level of
your React application's
hierarchy of modules

app.js
var params = {
};
This is the top level of
your React application's
hierarchy of modules
It makes use of the
qewd-react
loader to get everything
started

app.js
var params = {
};
You just define two things:

app.js
var params = {
};
The application name
This is the name that will
be used by ewd-xpress
to register it

app.js
var params = {
};
Your Application's effective
top-level Component
Referred to as MainPage
but your component file
can be named what you like
Note: you use
require() to load the file

MainPage.js
~/qewd/www/react-demo1/MainPage.js
"use strict"
return (
<div>
</div>
);
}
});
So as far as you're concerned,
this is your top component
By the time it is invoked,
EWD has started and
the application is
registered by QEWD

MainPage.js
"use strict"
return (
<div>
</div>
);
}
});
Here we're not doing
anything except displaying
this text

Then we bundled it
We told Browserify to start with app.js
It automatically threads its way down through any require() functions

Then we bundled it
We told Browserify to start with app.js
It automatically threads its way down through any require() functions
and combines all the JavaScript into a single file named bundle.js

So when we start the app
<head>
</head>
<body>
</body>
</html>
The index.html
file is loaded into
the browser, and it
then loads the
bundled JavaScript
file

And what we see is…

The application is registered

And displays the text defined
in your MainPage component

It's not doing much so far
"use strict"
return (
<div>
</div>
);
}
});
We'll start to build it out
in the next part of the course

It's not doing much so far
"use strict"
return (
<div>
</div>
);
}
});
We'll make it send a message
To QEWD and return
a response that we display
See the next part of this course

EWD 3 Training Course Part 37: Building a React.js application with ewd-xpress Part 1

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