Using dynamically generated checkboxes in Apex

In one of my projects, I’m building an application in Apex. This application depends entirely on webservices for its data. Which meant that I had to be smart in my design.
The project revolves around a system in which customers can create a survey. The survey is then presented to individuals using an Apex front-end. This means that all information on the front-end is shown dynamically.
One of the question types that is used, is presented using checkboxes. This proved to be quite a challenge in Application Express.
First of all I needed to understand the inner workings of Apex’s array collections. Normally an item in a form is put into a desired array using code like apex_item.hidden(1,value), which puts a value into array 1. So what I did in my project was to put all values in the form into an array and later select them by using a loop:

for i in 1 .. apex_application.g_F01.count
insert into answer_table (question, answer)
end loop;

But this is not the way to go with checkboxes, because a webbrowser only sends the checkboxes that are actually checked. This means that when you have a question with 5 possible answers and the user checks 2 of them, you get an array with 2 values per question. But because there is only one question, the arrays for question and answer go out of sync.
After browsing through the Oracle forums, I started to think of a solution to my specific problem.
What I eventually ended up with, was a specific array #40, just for questions with a checkbox. This array holds the question_id concatenated with the checkbox value and a letter X inbetween (because both the question_id and checkbox value are numbers, I can use any non-numeric character). This same array is filled with a hardcoded value for all other items, to distinguish them.
A simple textitem would look something like this:


And a checkbox item like this:

htp.p(apex_item.checkbox(40,question_id||'X'||choice_id,p_checked_values => l_select_list,p_checked_values_delimitor => ';'));

Now when I need to pick up these items in my page, I first form a loop like the one in the beginning of this post with an extra IF to check if APEX_APPLICATION.G_F03(i) is not ‘CHECKBOX’.
After that I go through an extra loop which gets all items in apex_application.g_F40.count and where this statement is true APEX_APPLICATION.G_F40(i) <> 'XXTESTVALUEXX'.
With a little help from instr, substr and replace I can then pull out the question_id and selected checkbox value from array #40.