Listing 2: The final version of edit-quizfile.pl.

#!/usr/bin/perl -w

use strict;
use diagnostics;
use CGI;        # Available from http://www.perl.com/CPAN
use [cw]QuizQuestion[ecw]s;

# Maximum number of questions in a quiz
my $MAX_QUESTIONS = 10;

# Default quizname
my $quizname = "";

# Create an instance of CGI
my $query = new CGI;

# Print the MIME header that we will always use
print $query->header("text/html");

# Determine how we were invoked
my $request_method = $query->request_method;

# ------------------------------------------------------------
# If we were invoked via POST, then save the changes

if ($request_method eq "POST")
{
    $quizname = $query->param("quizname");

    # Create an instance of QuizQuestions
    my $questions = new QuizQuestions($quizname);

    # Add questions to $questions
    my $counter = 0;

    foreach $counter (0 .. $MAX_QUESTIONS)
    {
	# Only handle as many questions as were filled in, by
	# checking to see if the question was entered
	last unless ($query->param("question-$counter") ne "$counter");

	# Set the question
	my @question = ($query->param("question-$counter"),
			$query->param("answer-a-$counter"),
			$query->param("answer-b-$counter"),
			$query->param("answer-c-$counter"),
			$query->param("answer-d-$counter"),
			$query->param("correct-$counter"));

	# Add the question to the quiz
	$questions->addQuestion(@question);
    }

    # Save the questions to disk
    my $result = $questions->saveFile;
    
    # If something went wrong, tell us what it was
    if ($result ne "0")
    {
	print $query->start_html(-title => "Error");
	print "<P>$result</P>\n";
	print $query->end_html;
	exit;
    }
}

# ------------------------------------------------------------
# If we were invoked using GET, then get the name of
# the quizfile

if ($request_method eq "GET")
{
    # If the query string is empty, then produce a page of HTML
    # containing ISINDEX 
    if ($query->param("keywords") eq "")
    {
	print $query->start_html(-title => "Enter a quiz name");
	print "<P>Please enter the name of the quiz you want ";
	print "to create or edit in the below .</P>\n";
	print "<ISINDEX>\n";
	print $query->end_html;

	exit;
    }
    else
    {
	# Get the name of the quiz
	$quizname = $query->param("keywords");
    }
}

# Whether we were invoked with GET or POST, display
# the current state of the quiz

# Create a new instance of QuizQuestions
my $questions = new QuizQuestions($quizname);

# Read the questions from disk, ignoring errors
# (since we will happily create a new quiz)
my $result = $questions->loadFile;

# Create the header for the HTML page
print $query->start_html(-title => "Create/Edit a quiz");

# Define a form
my $script_name = $query->script_name;
print "<Form method=\"POST\" action=\"$script_name\">\n";

# Create the text element for the quiz name
print "<P>Editing quiz: <input type=\"text\" name=\"quizname\" ";
print "value=\"$quizname\"></P>\n";
print "<HR>\n\n";

# Now create one form element for each existing question

my $counter = 0;
foreach $counter (0 .. $MAX_QUESTIONS)
{
    # Get a particular question
    my ($qtext, $ansA, $ansB, $ansC, $ansD, $correct)
	= $questions->getQuestion($counter);

    # Question text
    print "<H2>Question $counter</H2>\n";
    print "<P>Question text: <input type=\"text\" ";
    print "name=\"question-$counter\" value=\"$qtext\" ";
    print "size=\"30\"></P>\n";

    # Answer A
    print "<P>Answer A: <input type=\"text\" value=\"$ansA\" ";
    print "name=\"answer-a-$counter\" size=\"30\"></P>\n";

    # Answer B
    print "<P>Answer B: <input type=\"text\" value=\"$ansB\" ";
    print "name=\"answer-b-$counter\" size=\"30\"></P>\n";

    # Answer C
    print "<P>Answer C: <input type=\"text\" value=\"$ansC\" ";
    print "name=\"answer-c-$counter\" size=\"30\"></P>\n";

    # Answer D
    print "<P>Answer D: <input type=\"text\" value=\"$ansD\" ";
    print "name=\"answer-d-$counter\" size=\"30\"></P>\n";

    # Correct answer
    print "<P>Correct answer: <select name=\"correct-$counter\">\n";
    
    my $letter = "";
    foreach $letter ("a","b","c","d")
    {
	print "<option ";
	print "selected " if ($letter eq $correct);
	print "$letter>$letter\n";
    }

    print "</select>\n";
    print "<HR>\n\n";
}

# Now that the loop is complete, we can finish things up
print '<input type="submit" value="Save changes">', "\n";
print "</HTML>\n";
print $query->end_html;