A Cookbook.

The FormPanel widget in ExtJS does a real good job. It can be configured to validate complicated wired fields directly in the browser and has a clean, easy, and generic way to handle loading, checking and saving data through Ajax and JSON. Of course we want this widget in our Rails application. Luckily, Apotomo’s Extjs::FormPanel does all this.

Here’s a very simple example how to insert and customize such a FormPanel.

app/apotomo/apotomo_widget_tree.rb

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  w << my_form = cell(:my_first_form, :render_as_function, 'my_form',
    :object_id => 9)

We plug a cell widget into our application, and set it’s start state. I also explicitly set a static parameter (line 2) for demonstration purposes.

app/cells/my_first_form_cell.rb

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class MyFirstFormCell < Extjs::FormPanel
 
  def init_config
    config = super
    config[:title] = "My first cheap Form"
    config[:width] = 300
    config[:frame] = true
 
    config[:items] = [
      { :xtype      => :textfield, 
        :fieldLabel => "Some text", 
        :name       => "text_field"}]
  end
 
  def load_data
    id = param(:object_id)   # find out business object to edit.
    @obj = get_object_for(id)
    return @obj
  end
 
  # note that we already have the form business object in @obj.
  def process_data(data)
    if @obj.valid?(data[:text_field])
      # update and save @obj here, send an email, ...
 
      return valid_answer
    end
 
    return invalid_answer({:text_field => "not ok!"})
  end  
end

To customize the generic FormPanel we derive MyFirstFormCell (line 1). The easiest way to add some fields to the form is to provide their config in #init_config (line 9-12). If you think this is to coarse-grained (or static) and would like to add real Apotomo widgets like TextField, you can also go this way. But- more on that in another article.

Loading initial data
By overwriting the #load_data method, we can implement the way our form finds its data to edit (line 15-19). In this example, this method is called whenever the “Load” button in the form is clicked.

Processing the input
When overwriting the #process_data method we can hook into the form processing workflow and implement our own. It’s called after clicking “Save”. We already get the form input as a hash in the data parameter. It’s our time to check it here. We could e.g. pass it to ActiveRecord::update_attributes.
If we encounter validation errors on the server-side we can send those back to the ExtJS form with #invalid_answer (line 29).

Summary
The Extjs::FormPanel widget provides a quick but flexible way to integrate FormPanels in your applications, using pure Ruby. By overwriting methods you can easily build quite complex forms without having to worry about JavaScript and ExtJS events, since they’re mapped to Ruby via Apotomo.

This example was very generic and simple. It was meant to show the basic idea behind this cool widget.

When I want to separate similar parts of my application, I love to use “notebooks”, or tab panels. The users instantly notices that all of the tabs belong to one section of the application, but represent different areas of functionality. TabPanels in ExtJS additionaly have the nice behaviour to load their tab content on demand. Today I integrated this widget into Apotomo.

The setup is a Panel, containing a TabPanel. The first tab contains a TreePanel itself.

app/apotomo/apotomo_widget_tree.rb

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w << apnl = ext_panel('apotomo_panel', :title => "Apotomo rocks!", :width => 320)
  apnl << tbpanel = ext_tab_panel('my_tabpanel', :height => 90)
 
    tbpanel << tab1 = ext_tab('my_tab1', :title => "Wow!")
    tbpanel << tab2 = ext_tab('my_tab2', :title => "Give me some Panel")
 
      tab1 << tpanel = ext_tree_panel('an_ext_tree', :width => 200)
      tab2 << ext_panel('small_panel', :title => "Panel in Tab", :width => 180)

We just add one child, a Panel, to tab2 (line 8). Any number of widgets could be added here, e.g. a form widget, a news feed widget, or whatever you like.

When clicking on the second tab, ExtJS loads the content via AJAX by asking Apotomo for it.

The Tab widget isn’t directly mapped to an ExtJS widget, it was introduced for a better modularity and abstraction in Apotomo.

ExtJS’ TreePanel absolutely rock. You can display complicated data structures without worrying about the rendering process at all. However, what if you want to catch a click on a node and somehow process it in the Apotomo/Ruby environment?

In this example I’ll attach an event handler to a TreePanel which updates another widget whenever a node is clicked.

First we’ll have a look at the WidgetTree setup.

app/apotomo/apotomo_widget_tree.rb

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ts = Apotomo::TreeStore.new
ts[:root] = {:two=>{:two_one=>{}}, :three=>{}}
 
w << pnl = ext_panel('big_panel', :title => "Big Panel")
  pnl << tpanel = ext_tree_panel('an_ext_tree', :width => 200)    
    tpanel.set_store(ts)
 
  pnl << peer_panel = ext_panel('peer_panel', :title => "Tree peer", :width => 300)
    peer_panel << cell(:tree_peer, :init, 'my_tree_peer')
      tpanel.watch(:click, 'my_tree_peer', :_show_clicked)

When rendered, this leads to the following app state.

We can see the TreePanel widget and the “Peer Panel” widget being pushed into the “Big Panel” (line 5 and 8).

The my_tree_peer widget is in state :init, displaying a message that nothing special happened (line 9). If a click in the tree is encountered, my_tree_code is asked to go into the state :_show_clicked. (line 10).

Let’s click on a node.

In our new application state, the my_tree_peer widget reports which node was clicked. How spectacular! The Apotomo event dispatcher sent it to another state. We can find out how this new state works by looking at the widget code.

app/cells/tree_peer_cell.rb

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class TreePeerCell < Apotomo::StatefulWidget
 
  def transition_map
    { :init => [:_show_clicked],
      :_show_clicked => [:_show_clicked],
    }
  end
 
  def init
    "No item has been clicked."
  end
 
  def _show_clicked
    node_id = param(:node_id)
    "You clicked node #{node_id}."
  end
 
end

The two state methods just send static html to the screen, which is ok for demonstration purposes.

Note how we mapped a real ExtJS client-side event into a server-side Ruby event and managed all the event-handling in pure ruby. That’s Apotomo!