Mock Student Interface
by tdaxp ~ June 22nd, 2007
This morning’s accomplishments were buzzwordy. Using ruby on rails’ Ajax features I built a student interface to the web database that I set up yesterday. There were a couple hour-long periods of frustrating because I am still new to the language, but in the end I’m happy with what was done.
Ruby on Rails + Ajax
HTML special characters needed for putting this online are courtesy of HTML Special Character Converter
Having got the administration system running, now for student-side code.
First, create a “students” controller with a method “index” (94)
ruby script/generate controller students index
then in controllers/student_controller.rb, define the index method as such (95)
def index
@experiments = Experiment.find_experiments
end
and then within the model/experiments.rb, define the find_experiments function (96)
def self.find_experiments
find(:all, 
rder => “name” ).map {|u| [u.name, u.id]
end
and finally in views/students/index.rhtml (remember from yesterday)
<h1>Select your experiment</h1>
select :login, :experiment_id, @experiments
Create the code necessary for students sections (106)
rake db:sessions:create
and fron the same page, uncomment the following line from config/environment.rb:
config.action_controller.session_store = :active_record_store
this will have rubyonrails rely on the database, not the file session, to keep track of sessions. Now just rake db:migrate and restart the script/server to store the sessions!
The section on AJAX starts on page 128 of Agile Web Development with Rails — 2nd Edition, though I also used onlamp. So go back to the view/students/index.rhtml file and chang e it to be so (128-129):
<html>
<head>
<title>Notes on Rails Mock Student Interface</title>
<%= javascript_include_tag "prototype" %>
</head>
<body>
<h3>Add to list using Ajax</h3>
<%= form_remote_tag(:update => "login_with_condition",
:url => { :action => :select_condition_from_experiment },
:position => "top" ) %>
New item text:
<%= select :selected_experiment, :experiment_id, @experiments %>
<%= submit_tag "Select Experiment" %>
<%= end_form_tag %>
<div id="login_with_condition"></div>
</body>
</html>
while updating the controller:
def select_condition_from_experiment
selected_experiment_id = params[:selected_experiment][:experiment_id]
render_text "<li>" + selected_experiment_id + "</li>"
end
Now that this works, the next step is to dynamically generate a form that will allow us to select the condition. (Note that this isn’t a step-by-step tutorial — I’m noting mistakes that I made. This page is a thinking out loud excersize.)
Go to condition.rb and add a method self.find_conditions (this code adapted from rubyonrailsblog):
def self.find_conditions(selected_experiment_id)
@conditions = Condition.find(:all, :conditions => ['experiment_id = ?' , selected_experiment_id ] ).map {|u| [u.name, u.id] }
end
update select_condition_from_experiment like so:
def select_condition_from_experiment
@experiments = Experiment.find_experiments
selected_experiment_id = params[:selected_experiment][:experiment_id]
@conditions = Condition.find_conditions(selected_experiment_id)
render :partial => “select_condition”
end
And create a partial view titled app/views/students/_select_condition.rhtml that reads:
<%= form_remote_tag(:update => "notetaking_display",
:url => { :action => :select_notes_from_condition },
:position => "top" ) %>
New item text:
<%= select :selected_condition, :condition_id, @conditions %>
<%= submit_tag "Select Condition" %>
<%= end_form_tag %>
<div id="notetaking_display"></div>
Next up, create a select_notes_from_conditio module in the student controller
In app/models/notes_field.rb, add the following function
def self.find_by_condition(selected_condition_id)
@entries = find(:all, :conditions => ['condition_id = ?' , selected_condition_id ] )
end
But the exact same function in notes_record.rb, and add the following to students_controller.rb
def select_notes_from_condition
selected_condition_id = params[:selected_condition][:condition_id]
@notes_fields = NotesField.find_by_condition(selected_condition_id)
@notes_records = NotesRecord.find_by_condition(selected_condition_id)
render :partial => “notes_view”
end
Then in _notes_view.rhtml:
<h1>Note-Taking Matrix</h1>
<table border="1">
<tr>
<td> </td>
<% for notes_record in @notes_records %>
<td><%= h(notes_record.name) %></td>
<% end %>
</tr>
<% for notes_field in @notes_fields %>
<tr>
<td><%= notes_field.name %></td>
</tr>
<% end %>
</table>
Done for the day! Next up will be login in specific students and storing their notes.
I think this is your...
June 22nd, 2007 at 12:00 am
wait a minute. didn't you say once that Ajax was just some fad or you didn't like it or something?
June 23rd, 2007 at 12:00 am
About a year ago! [1]
I said that “Giving a stable technology a mystifying acronym may help on the marketing angle….But it's inherently deceptive. And dishonest. “
Indeed. And what's neat about Ajax under rails is that it's even more stable and less of an issue. The only difference between an ajax form and a standard form in ruby on rails is the function name and some other small things. There's no real clue that you're dealing with the XMLHttpRequest, Javascript, ajax, etc… because that's not needed. You just say, essentially, “I want a form that updates this section of a page” instead of “I want a form that updates the whole page.”
That is how technology should function: as intended, and not as a mystical collection of buzzwords.
[1] http://www.tdaxp.com/archive/2006/08/05/ajax-is-javascript-web-services.html
June 24th, 2007 at 12:00 am
a ha. thanks for the research and clarification