ruby-hyperloop.io/docs/tutorial.md at old_reactrb_master · ruby-hyperloop/ruby-hyperloop.io

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We'll be building a simple but realistic chat application, a basic version of a chat room offered by a service like gitter.im.

ChatRB Demo App

Our Chat app will provide:

A login window to register your chat handle
A view of the current chat conversation
An input box to submit a chat

It will also have a few neat features:

Live updates: other users' chats are popped into the conversation view in real time.
Dynamic Time Formatting: the time format changes as that chat ages.
Markdown formatting: users can use Markdown to format their text.
Uses Bootstrap: for styling

Let's Get Started!

open up a file named chatrb.html (or whatever you want)
copy in the following content and save it.
point your browser to file://...your directory path.../chatrb.html and you should see the current time.

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Hello React</title>
    <script src="https://code.jquery.com/jquery-2.1.4.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/marked/0.3.5/marked.min.js"></script>
    <script src="https://rawgit.com/reactrb/reactrb-express/master/reactrb-express.js"></script>
    <script src="https://reactrb.github.io/react/js/test_chat_service.js"></script>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap-theme.min.css" integrity="sha384-fLW2N01lMqjakBkx3l/M9EahuwpSfeNvV63J5ezn3uZzapT0u7EYsXMjQV+0En5r" crossorigin="anonymous">
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" crossorigin="anonymous"></script>

    <style type="text/css">
      /* most styles will come from bootstrap, but we will be adding a
        few extra styles here */
    </style>

    <script type="text/ruby">
      # Our ruby code will go here.  For now lets use a simple component
      # to make sure things are working.  For the rest of the tutorial
      # all the code we write will go in this section.
      class App < React::Component::Base
        before_mount { @timer = every(1) { force_update! } }
        def render
          "The current time is #{Time.now}"
        end
      end  
    </script>
  </head>
  <body>
    <!-- Tell inline reactive ruby to mount App here -->
    <div data-reactrb-mount="App"></div>
  </body>
</html>

Application Structure

React is all about modular, composable components. For our chat app, we'll have the following structure which will be mirrored by 6 corresponding Reactrb components:

App
  Nav
  Messages
    Message
      FormattedDiv
    Message
      FormattedDiv
    ... repeat for each ... message
  InputBox
    FormattedDiv

Each component will render the corresponding portion of the UI and is described by a Ruby class that inherits from React::Component::Base.

Let's stub out all of classes right now. Replace the contents inside the <script type="text/ruby">...</script> tag with the following ruby code.

class App < React::Component::Base
  def render
    div do
      Nav()
      Messages()
      InputBox()
    end
  end
end

class Nav < React::Component::Base
  def render
    div {"Our Nav Bar Goes Here including a login box"}
  end
end

class Messages < React::Component::Base
  def render
    # eventually we will loop and display each message
    # for now we will just display one as an example
    Message()
  end
end

class Message < React::Component::Base
  def render
    FormattedDiv()
  end
end

class InputBox < React::Component::Base
  def render
    div do
      "An input box to send new messages will".br
      "go here plus a display of the formatted markdown".br
      FormattedDiv()
    end
  end
end

class FormattedDiv < React::Component::Base
  def render
    "convert and display markdown"
  end
end

Refresh your page, and you should see this:

Our Nav Bar Goes Here including a login box
convert and display markdown
An input box to send new messages will
go here plus a display of the formatted markdown
convert and display markdown

Before going on lets understand the basic features of the Reactrb DSL

Every component has a render method

Each component is a class that inherits from React::Component::Base and defines a render method.
The render method must generate a single React::Element

Look at the App component: it wraps its three children in a div. If you forgot this wrapper div you would get this error in the browser's javascript console:
```
RuntimeError: a components render method must generate and return exactly 1 element or a string
```
HTML tags are Ruby methods

Within the render method each html tag has a corresponding Ruby method. Each of these methods generates a single React::Element, which contains component type plus parameters, plus any nested elements.

All HTML tags have lower case names matching their HTML counter parts, with the exception of the p tag, which is generated by the para method.
Application components also define Ruby methods

You generate a Message component by calling the Message() method

Because the component class and the component method share the same name you must include either (possibly empty) parenthesis, or block literal following the component name, so Ruby knows you mean to call a method.

Message <- a class name Message() <- generate a Message element.
By default strings are wrapped by span tags

Now go all the way down to the FormattedDiv component. If a string appears as the last expression (the returned value) of either a render method or a component's block, the string is wrapped in a span as if you had typed span { "some string" }.
Strings also respond to br, span, para, th and td

Strings also respond to several element generating methods: br, span, para (for p), td and th. Again this is just short hand, so "foo".td is short for td { "foo" }

Adding Parameters

Components have parameters just like methods. Now that we have the basic App structure, understanding a component's params is a good next step. Lets start by adding the markdown parameter to the FormattedDiv component.

Update the Message, InputBox and FormattedDiv components so they look like this:

class Message < React::Component::Base

  def render
    FormattedDiv(markdown: "This **Markdown** will eventually be a message")
  end
end

class InputBox < React::Component::Base
  def render
    div do
      "An input box to send new messages will".br
      "go here plus a display of the formatted markdown".br
      FormattedDiv(markdown: "This **Markdown** will get updated as the user types")
    end
  end
end

class FormattedDiv < React::Component::Base

  param :markdown, type: String

  def render
    div do
      params.markdown
    end
  end
end

The param macro describes the inputs to a component.

In our case the FormattedDiv component will receive the markdown param from either the Message or InputBox components.
Params can have an optional type.

In our case we declare markdown to be a String. If the incoming parameter does not match the type a warning will be displayed on the console. While typing your params is optional its highly recommended.
Params are accessed using the params object.

Each param you declare in a component will have a corresponding method on the params object. Component parameters are accessible by any instance method within your component using the params object.

Adding An Event Handler

Our application will need to respond to three types of events:

A user logs in
A user sends a chat
Receiving chat messages.

We will start by adding a basic user login handler.

We decided up front that the login box will be part of the top nav bar, so that is where we will add it:

class Nav < React::Component::Base

  def render
    div do
      input(class: :handle, type: :text, placeholder: "Enter Your Handle")
      button(type: :button) { "login!" }.on(:click) do
        alert("#{Element['input.handle'].value} logs in!")
      end
    end
  end

end

Replace the Nav component with the above code, and refresh your browser. You should now be able to "login".

Things to notice:

Event handlers are attached to any element using the on method.

The on method takes the event name and a block. The block is called when the event occurs.
Tag attributes are passed just like params.

input(class: :handle, type: :text, placeholder: "Enter Your Handle")
generates
<input class="handle", type="text", placeholder="Enter Your Handle" />
Strings and Symbols are the same type in Opal.

For effeciency the Opal-Ruby transpiler treats Ruby symbols as strings. So
:text == 'text'
Element is the Opal-Ruby jQuery compatible wrapper.

Element['input.handle'].value translates to $('input.handle').value()
Be aware that React::Element which we refer to as elements through out the tutorial is not the same as Opal's Element wrapper.

Adding State

Our improved Nav component is still pretty dull, and having to directly access the DOM using Element is not a great idea either.

To add some intelligence to our Nav component it needs state. Reactrb provides state variables that work like reactive instance variables. When a state variable is updated, it will cause components to re-render.

We are going to add two state variables to our component: current_user_name and user_name_input.

current_user_name is either nil (meaning there is no valid user name) or contains the user name string.

user_name_input will track the user name as it is typed allowing us to dynamically update the UI based on what the user has typed.

class Nav < React::Component::Base

  before_mount do
    state.current_user_name! nil
    state.user_name_input! ""
  end

  def render
    div do
      input(type: :text, value: state.user_name_input, placeholder: "Enter Your Handle"
      ).on(:change) do |e|
        state.user_name_input! e.target.value
      end
      button(type: :button) { "login!" }.on(:click) do
        login!
      end if valid_new_input?
    end
  end

  def valid_new_input?
    state.user_name_input.present? && state.user_name_input != state.current_user_name
  end

  def login!
    state.current_user_name! state.user_name_input
    puts "*** #{state.current_user_name} has logged in"
  end

end

Once again, update the Nav component, and make sure it works.

Things to notice:

State variables are accessed through the state object.

Each state variable has a read and write accessor on the state object. The write accessor ends with a "!" to remind you that this method will update state and cause re-rendering of the component.
There is no assignment method for state variables.

There are several reasons for this, that we will discuss later, but for now you can consider the write accessor (or bang method) to be equivalent to assignment.
Initialize state in the before_mount callback.

The before_mount lifecycle callback is called after params are first initialized, but before render is called, so its the place to initialize your state variables.

More on the lifecycle callbacks later.
Event handlers are passed the event object

As each character is typed we use the event object to update state.user_name_input.

Besides giving us dynamic access to the state of the user input as its changing, state.user_name_input also frees us from having to tag and interrogate DOM objects directly.
As state changes, the component will rerender.

For example the login button is only rendered if there is valid new input.

In React you think declaratively about the UI. At any point in time the render method simply draws the UI based on params and the current state of the component. As the component state changes, or when it receives new params, render is called to deliver the updated UI.

Under the hood React.js has efficient algorithms to insure that the minimum DOM update is performed.
Use helper methods to keep render simple.

For example we created the is_valid_new_input? method, and moved the login logic to the login! method.

This helps to understand the core logic and layout of the render method.
The puts method logs on the js debug console

Talking to Your Parents

We will add some other nice features of our Nav component later but right now we need to think about what happens when the user logs in.

We don't want to clutter up our Nav component with this logic so we need some way to communicate that we have a new user name upwards to the parent.

There are quite a few different ways to do this, depending on your specific needs. A straight forward way is for the parent to provide a callback that the Nav component will use to signal that a new user has logged in.

Add the following param declaration at the top of the Nav component:

  param :login, type: Proc

and update the login! method so it looks like this:

  def login!
    state.current_user_name! state.user_name_input
    params.login(state.user_name_input)
  end

Again reload your browser and try logging in. You will notice in the console that there is a new warning:

Warning: Failed propType: In component `Nav`
Required prop `login` was not specified Check the render method of `App`.

Which makes sense, as we specified that Nav wants a login parameter, but App did not provide one.

Lets go ahead and add the callback to the App component. Add the following method to the bottom of the App:

  def login(user_name)
    puts "*** #{user_name} has logged in"
  end

and pass the login method to the Nav component like so

  def render
    Nav(login: method(:login))
    ...
  end

Reload your browser, and login, and the warning will be gone, and the login message will be back.

Note: There will still be this warning:

Failed propType: You provided a `value` prop to a form field without an `onChange` handler.

which you may ignore.

Lets review these changes:

Callbacks are a simple way to communicate upwards

As we will see there are other mechanisms which are often more appropriate but in this case a call back Proc is the perfect solution.

To implement a callback you declare the param type as Proc. This tells the params object to treat the param as a method call, rather than just returning its value.

Meanwhile in the parent component you will need to pass a Proc to the component. Ruby lets you create and access Procs in several ways, in our case we converted the instance method login to a Proc using method.
React takes the approach of warning vs. errors when things go wrong

The good thing is this allows you some wiggle room as you are building and testing your components.

The downside is that you need to keep an eye on the console log, and find and remove unexpected warnings.

Before we go on note that this is an example application. In a real world app we would probably not use this mechanism for logging on. A real login component would need to check credentials and would have additional state to track and report the progress of the login process.

The Chat Service

Now that we can login, its time to understand the chat service. Lucky for us Heroku already has a demo chat application that we will use. Thanks Heroku! To keep things focused on React, we have already included a Ruby wrapper that our application will use.

To access the Chat Service we create a new instance of the ChatService like this:

  chat = ChatService.new do | messages |
    # After a user logs in, a (possibly empty) initial
    # array of current messages will be sent to this block.
    # As new messages arrive the block will be called again.  
  end

The object returned by ChatService.new has three methods: login, id and send.

  chat.login("LukeS") # login user "LukeS" - for our simple app no password is Required
  chat.id             # returns the current id (i.e. "LukeS")
  chat.send(message)  # sends message to everybody (including the sender)

What the message contains is completely up to us. We will be sending hashes containing the sender's handle, the message string, and the time that the message was sent:

  chat.send({handle: ..., message: ..., time: Time.now})

And finally the authors of our ChatService class have provided us with a test service preloaded with a set of messages in our chosen format. We are already including this version in our header.

Armed with this, we are ready to start displaying chat messages.

Lifecycle Callbacks

A react component has a well defined life cycle, and your components can hook into the lifecycle using the callback macros. In our application we will use three of the most common callbacks before_mount, after_mount and after_update.

Each call back takes a block or the name of a method, which will be called as the component passes through each stage in its lifecycle.

When our App starts (mounts in React terms) we need to initialize the chat service.

Add this code to the beginning of the App component:

  before_mount do
    ChatService.new do | messages |
      if state.messages
        state.messages! state.messages + messages
      else
        state.messages! messages
      end
      puts "state messages updated.  state.messages: #{state.messages}"
    end
  end

Before the component mounts our callback will execute and it creates a new ChatService instance.

As each new set of messages arrives the block will execute which will initialize or append the messages to the state.messages state variable. We know we want to make this a state variable since it clearly is going to change asynchronously overtime, and we will want to update the UI when that occurs.

Refresh your browser, and make sure nothing is broken, but notice nothing is changing. Why Not? - because we have not logged in yet.

Instance and State Variables

Okay so while we can initialize the chat service when App mounts, nothing will happen until the user logs in.

We have our login method already defined, so we just want to change it so that it passes the login to the chat service. To do this we have to save the chat service object in the before_mount callback so that we can use it in the login method.

Change the before_mount callback to be:

  before_mount do
    @chat_service = ChatService.new do | messages |
      state.messages! ((state.messages || []) + messages)
      puts "state messages updated.  state.messages: #{state.messages}"
    end
  end

Now that we have saved our new ChatService object in @chat_service we can use it in the login method like this:

  def login(user_name)
    @chat_service.login(user_name)
  end

With this in place refresh your browser, and watch the console as you login. You should see an array of messages that looks like this:

state messages updated.  state.messages: {"from"=>"user1", "time"=>1449089985, "message"=>"A 2 point message: \n+ point 1\n+ point 2\nGot it?"},{"from"=>"user2", "time"=>1449262785, "message"=>"message sent 8 days ago, by user 2"},{"from"=>"user3", "time"=>1449521985, "message"=>"message sent in the last week"},{"from"=>"user2", "time"=>1449608385, "message"=>"message sent **also** in the last week"},{"from"=>"user1", "time"=>1449950385, "message"=>"Was sent within the last hour!"},{"from"=>"user2", "time"=>1449952185, "message"=>"Was sent 30 minutes ago"},{"from"=>"user3", "time"=>1449953385, "message"=>"Was just sent\n\n\n\n\n\n\n\n\nwith a lot of blanks"},{"from"=>"user1", "time"=>1449953985, "message"=>"just now"}

There is an important point here:

Not everything has to be a state variable

@chat_service is an instance variable, while state.messages is a state variable.

We can see that as time passes new messages will come in, and we will want to re-render when this happens. This led us to define messages as a state variable. Because messages is a state variable as it changes re-rendering of the App component will automatically occur.

But so far we have no reason to make @chat_service into a state variable, so we use a plain old instance variable.

For our simple component the messages themselves are the only state we care about.

We will come back to this discussion as we flesh out the rest of our application.

Now that we are logging in, connecting to the (test) chat service and updating our messages state variable, we are ready to display those messages.

Hopefully by this time you've got a rough idea how we are going to do this!

First update the App render method like this:

  def render
    div do
      Nav login: method(:login)
      Messages messages: state.messages
      InputBox()
    end
  end

Then add the corresponding messages parameter to the Messages component:

  param :messages, type: [Hash]

And update the Messages render method to iterate through all the messages displaying Message for each one:

  def render
    div do
      params.messages.each do |message|
        Message message: message
      end
    end
  end

Likewise the Message component needs to receive and display a message. Replace the whole component with the following:

class Message < React::Component::Base

  param :message, type: Hash

  def render
    div do
      div { params.message[:from] }
      FormattedDiv markdown: params.message[:message]
      div { Time.at(params.message[:time]).to_s }
    end
  end
end

Save everything, and refresh your browser. Login and you should see a very rough but functional display of your messages!

Array type params

Notice how we declared the messages param as type [Hash] this notation means "Array of Hash".

You can also say type: [] which means array of anything and is shorthand for type: Array.

Some Cleanup

Take a look at the console log, and you will see a big red error like this:

Exception raised while rendering #<Messages:0x16fa>
NoMethodError: undefined method 'each' for nil

Lets think about this. When we first render Messages, there are no messages, so trying to send each to nil fails.

One nice thing about React is that it is very robust. Even though we had this error, things still work. Once we are logged in, we do have messages, and everything worked.

Anyway we need to fix this! Add the following method to the bottom of the App class:

  def online?
    state.messages
  end

For our simple App we are going to figure that we are logged in if state.messages is not nil.

Now update the Apps render method so that we don't display the Messages or the InputBox unless we are logged in.

  def render
    div do
      Nav login: method(:login)
      if online?
        Messages messages: state.messages
        InputBox()
      end
    end
  end

Refresh the page and the error should be gone.

Sending Messages

Next lets send some messages. To do this the InputBox component will need to communicate when the user sends a new message. We could add a callback like we did with the Nav component, but it might be more appropriate to use a different mechanism here.

We know we can send a message by doing a @chat_service.send, so if we just pass the @chat_service down to the InputBox we should be all set.

So first update the App render method to pass the @chat_service to the InputBox:

   ...
   InputBox chat_service: @chat_service
   ...

Now update the InputBox like this:

class InputBox < React::Component::Base

  param :chat_service, type: ChatService

  before_mount { state.composition! "" }

  def render
    div do
      div {"Say Something: "}
      input(value: state.composition).on(:change) do |e|
        state.composition! e.target.value
      end.on(:key_down) do |e|
        send_message if is_send_key?(e)
      end
      FormattedDiv markdown: state.composition
    end
  end

  def is_send_key?(e)
    (e.char_code == 13 || e.key_code == 13)
  end

  def send_message
    params.chat_service.send(
      message: state.composition!(""),
      time: Time.now.to_i,
      from: params.chat_service.id
    )
  end

end

While we have done almost nothing new here, lets walk through so we are sure we understand everything.

The InputBox receives a ChatService which it will use to get the current user id, and send each new chat message.

The InputBox has one state variable state.composition which just keeps track of the current message as the user types, just like we did with the Nav component.

Instead of a "send" button, we just wait till the user hits the Enter Key.

The current value ofstate.composition is passed along to the FormattedDiv which will (eventually) display the formatted markdown.

Updating state variables returns the current value

Unlike the assignment operator, when you update a state variable you get back the current value of the state. Thus we can write state.composition!("") to clear the composition, while returning its current value.

Formatting The Markdown

Lets get the FormattedDiv working. The header loads the marked.js library which will convert markdown to html. React will normally escape any raw html, but there is a special escape mechanism which we will use in our component.

We will also use Opal-Ruby's native escape mechanism to insert raw javascript code so we can call the marked function.

Replace FormattedDiv's render method with the following:

  def render
    div do
      div({dangerously_set_inner_HTML: { __html: `marked(#{params.markdown}, {sanitize: true})`}})
    end
  end

Save your file, refresh, and login, and you should see the test messages as formatted html.

For more fun type some markdown into the input box and the formatted version will update as you type.

Inserting raw HTML

React makes this hard because its dangerous. The above syntax can be used whenever you need to directly insert some raw HTML.
Opal Javascript Native

In the above example we insert some raw javascript using the backquote literal. Within the literal you can escape back out to Ruby using the #{} operator.

Congratulations your chat app is basically working. If you want change test_chat_service.js to chat_service.js and you can now run your client in several windows and watch things update nicely.

Styling the App

We have a few more features to add, and if you have been observant you have noticed some bugs, but lets take a break and add some styling to our application.

We will use Bootstrap styles, which has already been included. We just need a few additional styles so lets add those now to the inline style sheet at the top of your HTML file:

  body {
    padding-top: 50px;
    padding-bottom: 60px;
  }
  div.alternating:nth-of-type(odd) {
    background-color: #ddd;
  }
  div.alternating:nth-of-type(even) {
    background-color: #ccc;
  }
  .input-box {
    padding: 10px;
  }
  .white {
    color: white;
  }
  .message {
    padding-top: 10px;
  }
  textarea {
    width: 100%;;
  }
  div.reactrb-icon {
    float: left;
    width: 50px;
    height: 50px;
    margin-right: 8px;
    background-size: contain;
    background-image: url("http://reactrb.github.io/react/img/logo_svg.png");
}

In Reactrb you can add classes to elements using css dot notation.

So instead of saying div(class: "foo bar") you can say div.foo.bar

Any dashes in class names should be translated to underscores. For example:

div.navbar.navbar_inverse.navbar_fixed_top is the same as div(class: "navbar navbar-inverse navbar-fixed-top")

With this we are ready to beautify our Nav component. Replace the render method with the following code.

  def render
    div.navbar.navbar_inverse.navbar_fixed_top do
      div.container do
        div.collapse.navbar_collapse(id: "navbar") do
          form.navbar_form.navbar_left(role: :search) do
            div.form_group do
              input.form_control(type: :text, value: state.user_name_input, placeholder: "Enter Your Handle"
              ).on(:change) do |e|
                state.user_name_input! e.target.value
              end
              button.btn.btn_default(type: :button) { "login!" }.on(:click) do
                login!
              end if valid_new_input?
            end
          end
        end
      end
    end
  end

While this looks complicated notice that in the middle is our original input tag. We have just added wrappers around it, and added the form_control class to the input, and the btn and btn-default classes to the login button.

Refresh you browser and things should start looking better already.

Lets move on to the Message and Messages components. First add the class container to the Messages div. The Messages render method should now look like this:

  def render
    div.container do # add the bootstrap .container class here.
      params.messages.each do |message|
        Message user_id: params.chat_service.id, message: message
      end
    end
  end

Now add the row, alternating and message classes to the outer div of the Message component, and the col-sm-2 class to the sender and time divs. (Remember to change dashes to underscores.)

Now add the class: "col-sm-8" to the FormattedDiv element. Notice that you can not use the short hand syntax with application defined components.

Your Message render method should look like this:

  def render
    div.row.alternating.message do
      div.col_sm_2 { params.message[:from] }
      FormattedDiv class: "col-sm-8", markdown: params.message[:message]
      div.col_sm_2 { Time.at(params.message[:time]).to_s }
    end
  end

Finally we need to update FormattedDiv so that it accepts all the normal html attributes uses them in the outer div. This will allow us to specify different style classes for the FormattedDiv in the message display and in the input box.

The collect_other_params_as macro is used to gather up any params not specified in param declarations and save them in a hash. This can then be passed along to children components (in our case the outer div) as their attributes.

Update the FormattedDiv render method so it looks like this:

class FormattedDiv < React::Component::Base

  param :markdown, type: String
  collect_other_params_as :attributes

  def render
    div(params.attributes) do # send whatever class is specified on to the outer div
      div({dangerously_set_inner_HTML: { __html: `marked(#{params.markdown}, {sanitize: true })`}})
    end
  end
end

Okay refresh your browser, and login, and things should be looking pretty good.

Lets continue on, and update the InputBox component.

Add the row, form-group, input-box, navbar, navbar-inverse, navbar-fixed-bottom classes to the outer div.

Add the col-sm-1 and white classes to the "Say Something" div.

Add the col-sm-5 class to the input

Finally add class: "col-sm-5 white" to the FormattedDiv element.

Your updated render method should look like this:

  def render
    div.row.form_group.input_box.navbar.navbar_inverse.navbar_fixed_bottom do
      div.col_sm_1.white {"Say Something: "}
      input.col_sm_5(value: state.composition).on(:change) do |e|
        state.composition! e.target.value
      end.on(:key_down) do |e|
        send_message if is_send_key?(e)
      end
      FormattedDiv class: "col-sm-5 white", markdown: state.composition
    end
  end

Multiline Inputs

Now that our app looks better, we are motivated to clean up the remaining problems. First off our InputBox only lets us enter single lines. Lets fix that!

First change the input element to a textarea element which will allow us to display multiple lines.

Now go back and change the expression in the `is_send_key?`` method to also check for a ctrl or meta key.

  def is_send_key?(e)
    (e.char_code == 13 || e.key_code == 13) && (e.meta_key || e.ctrl_key)
  end

Try it out in your browser. You should now be able to enter multiple line inputs.

Its still not quite perfect. If you type more than two lines it gets hard to see our text. We would like the text box to expand as more lines are typed up to some maximum.

All we need to do is add the rows attribute to the textarea and calculate the rows based on the current number of lines in the text area box.

Add this method right after the render method:

  def rows
    [state.composition.count("\n") + 1,20].min
  end

and pass the value of our new rows method to the rows attribute of the textarea:

  textarea.col_sm_5(rows: rows, value: state.composition)...

Refresh and you should be see the textarea dynamically grow as you type more text, and then collapse when you send a message.

This brings up a very important point about states:

Where possible compute values rather than adding state

You might be tempted to create a state variable called rows that is updated whenever the text area changes.

This may (or may not) be slightly more effecient, but it introduces a lot of complexity.

Instead where ever possible compute values from existing state.

Automatic Scroll Position

You may have noticed that when you enter a message, you can't see it until you scroll down. We would like to automatically scroll down when a message is sent so you can see it. While we are at it, we will also make any new incoming messages do the same thing.

Displaying the messages is the responsibility of the Messages component so that is where this fix will go.

First add this method to the bottom of the Messages component:

  def scroll_to_bottom
    Element['html, body'].animate({scrollTop: Element[Document].height}, :slow)
  end

Now all we need to do is call scroll_to_bottom whenever our message data changes. What we need to do is hook into the after_mount, and after_update callbacks. after_mount runs after the initial rendering of a component, and likewise after_update runs after every subsequent update.

Add these two lines right after the param declaration in the Message component:

  after_mount :scroll_to_bottom
  after_update :scroll_to_bottom

Notice that instead of providing a block to the callbacks we are providing the name of a method to call, which is handy in this case since we want to use the same method twice.

After making these changes you will see that after any update to the message display the window is scrolled to the bottom.

Detecting the Logged In User

The display is a bit impersonal. If I am logged in, then messages from me should say "You" instead of my login name.

Lets fix this.

Add this method to the bottom of the Message component:

def sender
  if params.message[:from] == params.user_id
    "you: "
  else
    "#{params.message[:from]}:"
  end
end

and replace params.message[:from] in the render method with sender.

But we have to pass the user_id down from the App component (@chat_service.id) to Messages, and from Messages to Message. Once you have added the params and passed them along, refresh your browser.

If you are still using the test fixture then login as user1 and see the results.

Formatting The Time Stamp

While we are fixing the Message component lets clean up the time stamp column. The time stamp is not only ugly, its also not informative. Lets make it so it progressively changes formats the older the message gets.

Add this method to the bottom of the Message component:

def formatted_time
  time = Time.at(params.message[:time])
  if Time.now < time+1.day
    time.strftime("%I:%M %p")
  elsif Time.now < time+7.days
    time.strftime("%A")
  else
    time.strftime("%D %I:%M %p")
  end
end

and then call formatted_time instead of just displaying the raw time.

A Final Bug Fix

Try logging in, and then logging in again, either as the same or different user. Notice that the list of messages is duplicated.

Our chat service supplies us with all existing messages when somebody logs in. And our App component happily appends all the incoming messages.

What we need to do is clear the messages during the login process.

Add this line at the beginning of the App login method:

  ...
  state.messages! nil
  ...

Make sure you do this before sending the credentials to the chat service.

Final Touches

You may notice that you can't hit the enter key to login. Instead the enter key refreshes the page.

To fix this the Nav component will need to two additional event handlers, one to track the key_down event, and the other to clear the submit event for the form.

Add this handler to the input element:

  on(:key_down) do |e|
    login! if valid_new_input? && e.key_code == 13
  end

and add this handler to the form.

  on(:submit) { |e| e.prevent_default }

While we are in there lets add the Reactrb logo and a title to the nav bar. Add

  div.navbar_header do
    div.reactrb_icon
    a.navbar_brand(href: "#", style: {color: "#00d8ff"}) { "Reactrb Chat Room " }
  end

inside the container div.

Finally lets use one of the standard bootstrap login icons instead of the words "Login!".

Replace { "Login!" } with { span.glyphicon.glyphicon_log_in }

Now the completed Nav render method will look like this:

  def render
    div.navbar.navbar_inverse.navbar_fixed_top do
      div.container do
        div.navbar_header do
          div.reactrb_icon
          a.navbar_brand(href: "#", style: {color: "#00d8ff"}) { "Reactrb Chat Room " }
        end
        div.collapse.navbar_collapse(id: "navbar") do
          form.navbar_form.navbar_left(role: :search) do
            div.form_group do
              input.form_control(type: :text, value: state.user_name_input, placeholder: "Enter Your Handle"
              ).on(:change) do |e|
                state.user_name_input! e.target.value
              end.on(:key_down) do |e|
                login! if valid_new_input? && e.key_code == 13
              end
              button.btn.btn_default(type: :button) { span.glyphicon.glyphicon_log_in }.on(:click) do
                login!
              end if valid_new_input?
            end
          end.on(:submit) { |e| e.prevent_default }
        end
      end
    end
  end

Now that you are all done make sure you change from the test fixture so your app interacts with the webservice.

Update this line in the html header

<script src="https://reactrb.github.io/react/js/test_chat_service.js"></script>

to read

<script src="https://reactrb.github.io/react/js/chat_service.js"></script>

and you will be sending and receiving messages from the chat server. Try opening your a second browser window to get the full experience.

Congratulations

You have built a very nice functional application. We hope you have enjoyed the process. Happy Coding!

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Let's Get Started!

Application Structure

Every component has a render method

The render method must generate a single React::Element

HTML tags are Ruby methods

Application components also define Ruby methods

By default strings are wrapped by span tags

Strings also respond to br, span, para, th and td

Adding Parameters

The param macro describes the inputs to a component.

Params can have an optional type.

Params are accessed using the params object.

Adding An Event Handler

Event handlers are attached to any element using the on method.

Tag attributes are passed just like params.

Strings and Symbols are the same type in Opal.

Element is the Opal-Ruby jQuery compatible wrapper.

Adding State

State variables are accessed through the state object.

There is no assignment method for state variables.

Initialize state in the before_mount callback.

Event handlers are passed the event object

As state changes, the component will rerender.

Use helper methods to keep render simple.

The puts method logs on the js debug console

Talking to Your Parents

Callbacks are a simple way to communicate upwards

React takes the approach of warning vs. errors when things go wrong

The Chat Service

Lifecycle Callbacks

Instance and State Variables

Not everything has to be a state variable

Array type params

Some Cleanup

Sending Messages

Updating state variables returns the current value

Formatting The Markdown

Inserting raw HTML

Opal Javascript Native

Styling the App

Multiline Inputs

Where possible compute values rather than adding state

Automatic Scroll Position

Detecting the Logged In User

Formatting The Time Stamp

A Final Bug Fix

Final Touches

Every component has a `render` method

The `render` method must generate a single `React::Element`

By default strings are wrapped by `span` tags

Strings also respond to `br, span, para, th` and `td`

The `param` macro describes the inputs to a component.

Params are accessed using the `params` object.

Event handlers are attached to any element using the `on` method.

`Element` is the Opal-Ruby jQuery compatible wrapper.

State variables are accessed through the `state` object.

Initialize state in the `before_mount` callback.

Use helper methods to keep `render` simple.

The `puts` method logs on the js debug console