Isolated Component API

Matestack's concept of isolated components has a lot in common with async components. Isolated components can be deferred or asynchronously rerendered like async components. In difference to async components, isolated components are resolved completely independently from the rest of the UI. If an isolated component gets rerendered or loaded, Matestack will directly render this component without touching the surrounding UI implementation. async - in contrast - is executing the surrounding UI implementation in order to render the relevant UI part. On complex UIs this makes a difference performance wise!

Differences to simple components

Your isolated components can by design not

• yield components passed in by using a block

• yield slots passed in by using slots

• simply get options injected by surrounding context

They are meant to be isolated and resolve all data independently! That's why they can be rendered completely separate from the rest of the UI.

Furthermore isolated components have to be authorized independently. See below.

Differences to the async component

The async component offers pretty similar functionalities enabling you to define asynchronous rendering. The important difference is that rerendering an async component requires resolving the whole page on the serverside, which can be performance critical on complex pages. An isolated component bypasses the page and can therefore offer high performance rerendering.

Using the async component does NOT require you to create a custom component:

class Home < Matestack::Ui::Page
  def response
    h1 'Welcome'
    async id: "some-unique-id", rerender_on: "some-event" do
      div id: 'my-async-wrapper' do
        plain I18n.l(DateTime.now)
      end
    end
  end
end

Using an isolated component does require you to create a custom component:

class Home < Matestack::Ui::Page
  def response
    h1 'Welcome'
    MyIsolatedComponent.call(rerender_on: "some-event")
  end
end

Isolated components should be used on complex UIs where async rerendering would be performance critical or you simply wish to create cleaner and more decoupled code.

To create an isolated component you need to create a component which inherits from Matestack::Ui::IsolatedComponent. Implementing your component is straight forward. As always you implement a response method which defines what gets rendered.

class MyIsolatedComponent < IsolatedComponent

  def response
    div class: 'time' do
      paragraph text: DateTime.now
    end
  end

  def authorized?
    true
  end

end

And use it with the :defer or :rerender_on options which work the same on async components.

def response
  MyIsolatedComponent.call(defer: 1000, rerender_on: 'update-time')
end

Authorize

When asynchronously rendering isolated components, these HTTP calls are actually processed by the controller action responsible for the corresponding page rendering. One might think, that the optional authorization and authentication rules of that controller action should therefore be enough for securing isolated component rendering.

But that's not true. It would be possible to hijack public controller actions without any authorization in place and request isolated components which are only meant to be rendered within a secured context.

That's why we enforce the usage of the authorized? method to make sure, all isolated components take care of their authorization themselves.

If authorized? returns true, the component will be rendered. If it returns false, the component will not be rendered.

This might sound complicated, but it is not. For example using devise you can access the controller helper current_user inside your isolated component, making authorization implementations as easy as:

def authorized?
  current_user.present?
end

A public isolated component therefore needs an authorized? method simply returning true.

You can create your own isolated base components with their authorized methods for your use cases and thus keep your code DRY.

Options

All options below are meant to be injected to your isolated component like:

class Home < Matestack::Ui::Page
  def response
    heading size: 1, text: 'Welcome'
    MyIsolatedComonent.call(defer: 1000, #...)
  end
end

defer

The option defer lets you delay the initial component rendering. If you set defer to a positive integer or true the isolate component will not be rendered on initial page load. Instead it will be rendered with an asynchronous request only resolving the isolate component.

If defer is set to true the asynchronous requests gets triggered as soon as the initial page is loaded.

If defer is set to a positive integer (including zero) the asynchronous request is delayed by the given amount in ms.

rerender_on

The rerender_on options lets you define events on which the component will be rerenderd asynchronously. Events on which the component should be rerendered are specified via a comma seperated string, for example rerender_on: 'event_one, event_two.

rerender_delay

The rerender_delay option lets you specify a delay in ms after which the asynchronous request is emitted to rerender the component. It can for example be used to smooth out loading animations, preventing flickering in the UI for fast responses.

init_on

With init_on you can specify events on which the isolate components gets initialized. Specify events on which the component should be initially rendered via a comma seperated string. When receiving a matching event the isolate component is rendered asynchronously. If you also specified the defer option the asynchronous rerendering call will be delayed by the given time in ms of the defer option. If defer is set to true the rendering will not be delayed.

public_options

You can pass data as a hash to your custom isolate component with the public_options option. This data is inside the isolate component accessible via a hash with indifferent access, for example public_options[:item_id]. All data contained in the public_options will be passed as json to the corresponding Vue.js component, which means this data is visible on the client side as it is rendered in the Vue.js component config. So be careful what data you pass into public_options!

Due to the isolation of the component the data needs to be stored on the client side as to encapsulate the component from the rest of the UI. For example: You want to render a collection of models in single components which should be able to rerender asynchronously without rerendering the whole UI. Since we do not rerender the whole UI there is no way the component can know which of the models it should rerender. Therefore passing for example the id in the public_options hash gives you the possibility to access the id in an async request and fetch the model again for rerendering. See below for examples.

DOM structure, loading state and animations

Isolated components will be wrapped by a DOM structure like this:

<div class="matestack-isolated-component-container">
  <div class="matestack-isolated-component-wrapper">
    <div class="matestack-isolated-component-root" >
      hello!
    </div>
  </div>
</div>

During async rendering a loading class will automatically be applied, which can be used for CSS styling and animations:

<div class="matestack-isolated-component-container loading">
  <div class="matestack-isolated-component-wrapper loading">
    <div class="matestack-isolated-component-root" >
      hello!
    </div>
  </div>
</div>

Additionally you can define a loading_state_element within the component class like:

class MyIsolatedComponent < Matestack::Ui::IsolatedComponent
  def response
    div id: 'my-isolated-wrapper' do
      plain "hello"
    end
  end

  def authorized?
    true
  end

  def loading_state_element
    div class: "loading-spinner" do
      plain "spinner..."
    end
  end
end

which will then render to:

<div class="matestack-isolated-component-container">
  <div class="loading-state-element-wrapper">
    <div class="loading-spinner">
      spinner...
    </div>
  </div>
  <div class="matestack-isolated-component-wrapper">
    <div class="matestack-isolated-component-root">
      <div id="my-isolated-wrapper">
        hello!
      </div>
    </div>
  </div>
</div>

and during async rendering request:

<div class="matestack-isolated-component-container loading">
  <div class="loading-state-element-wrapper loading">
    <div class="loading-spinner">
      spinner...
    </div>
  </div>
  <div class="matestack-isolated-component-wrapper loading">
    <div class="matestack-isolated-component-root" >
      hello!
    </div>
  </div>
</div>

Examples

Simple Isolate

Create a custom component inheriting from the isolate component

class MyIsolatedComponent < Matestack::Ui::IsolatedComponent

  def response
    div id: 'my-isolated-wrapper' do
      plain I18n.l(DateTime.now)
    end
  end

  def authorized?
    true
    # check access here using current_user for example when using Devise
    # true means, this isolated component is public
  end

end

And use it on your page

class Home < Matestack::Ui::Page

  def response
    h1 'Welcome'
    MyIsolatedComponent.call()
  end

end

This will render a h1 with the content welcome and the localized current datetime inside the isolated component. The isolated component gets rendered with the initial page load, because the defer options is not set.

Simple Deferred Isolated

class Home < Matestack::Ui::Page

  def response
    h1 'Welcome'
    MyIsolatedComponent.call(defer: true)
    MyIsolatedComponent.call(defer: 2000)
  end

end

By specifying the defer option both calls to the custom isolated components will not get rendered on initial page load. Instead the component with defer: true will get rendered as soon as the initial page load is done and the component with defer: 2000 will be rendered 2000ms after the initial page load is done. Which means that the second component will show the datetime with 2s more on the clock then the first one.

Rerender On Isolate Component

class Home < Matestack::Ui::Page

  def response
    h1 'Welcome'
    MyIsolatedComponent.call(rerender_on: 'update_time')
    onclick emit: 'update_time' do
      button 'Update Time!'
    end
  end

end

rerender_on: 'update_time' tells the custom isolated component to rerender its content asynchronously whenever the event update_time is emitted. In this case every time the button is pressed the event is emitted and the isolated component gets rerendered, showing the new timestamp afterwards. In contrast to async components only the MyIsolated component is rendered on the server side instead of the whole UI.

Rerender Isolated Component with a delay

class Home < Matestack::Ui::Page

  def response
    h1 'Welcome'
    MyIsolatedComponent.call(rerender_on: 'update_time', rerender_delay: 300)
    onclick emit: 'update_time' do
      button 'Update Time!'
    end
  end

end

The MyIsolated component will be rerendered 300ms after the update_time event is emitted

Initialize isolated component on a event

class Home < Matestack::Ui::Page

  def response
   h1 'Welcome'
    MyIsolatedComponent.call(init_on: 'init_time')
    onclick emit: 'init_time' do
      button 'Init Time!'
    end
  end

end

With init_on: 'init_time' you can specify an event on which the isolated component should be initialized. When you click the button the event init_time is emitted and the isolated component asynchronously requests its content.

Use custom data in isolated components

Like described above it is possible to use custom data in your isolated components. Just pass them as a hash to public_options and use them in your isolated component. Be careful, because public_options are visible in the raw html response from the server as they get passed to a Vue.js component.

Lets render a collection of models and each of them should rerender when a user clicks a corresponding refresh button. Our model is called Match, representing a soccer match. It has an attribute called score with the current match score.

At first we create a custom isolated component.

class Components::Match::IsolatedScore < Matestack::Ui::IsolatedComponent

  def prepare
    @match = Match.find_by(public_options[:id])
  end

  def response
    div class: 'score' do
      plain @match.score
    end
    onclick emit: "update_match_#{@match.id}" do
      button 'Refresh'
    end
  end

  def authorized?
    true
    # check access here using current_user for example when using Devise
    # true means, this isolated component is public
  end

end

Now we create our page which will render a list of matches.

class Match::Pages::Index < Matestack::Ui::Page

  def response
    Match.all.each do |match|
      Components::Match::IsolatedScore.call(public_options: { id: match.id }, rerender_on: "update_match_#{match.id}")
    end
  end

end

This page will render a match_isolated_score component for each match. If one of the isolated components gets rerendered we need the id in order to fetch the correct match. Because the server only resolves the isolated component instead of the whole UI it does not know which match exactly is requested unless the client requests a rerender with the match id. This is why public_options options are passed to the client side Vue.js component. So if match two should be rerendered the client requests the match_isolated_score component with public_options: { id: 2 }. With this information our isolated component can fetch the match and rerender itself.