Math drupal module - drupal-7

Question

I'm trying to learn to write drupal modules and am working on writing a simple math module http://nodeone.se/en/the-math-question-module
I've got the GUI down fine but seem to be having issues with the actual math. I never seem to get the correct answer because I think it loads a new set of questions before it checks the current answer.
Here's what I have so far:
<?php
/**
* #file
* Tests users on their math skills through a series of question and answers
*/
/**
* Implements hook_menu().
*/
function math_question_menu() {
// add new navigation menu item
$items['math_question'] = array(
'title' => 'Math questions',
'description' => 'Test you math skills with these questions.',
'page callback' => 'drupal_get_form',
'page arguments' => array('math_question_page'),
'access callback' => 'user_access',
'access arguments' => array('administer_site_configuration'),
);
return $items;
}
$val1 = rand(1,10);
$val2 = rand(1,10);
variable_set('val1', $val1);
variable_set('val2', $val2);
/**
* Builds the form for configuring Math Questions.
*/
function math_question_page() {
global $user;
$num1 = variable_get('val1');
$num2 = variable_get('val2');
$total = $num1 + $num2;
variable_set('total',$total);
$form['math_question'] = array(
'#type' => 'item',
'#markup' => 'What is ' . $num1 . ' + ' . $num2 . ', ' .
check_plain($user->name) . '?',
);
$form['answer'] = array(
'#type' => 'textfield',
'#title' => t('Answer'),
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Check my answer'),
);
return $form;
}
function math_question_page_validate($form, $form_state) {
if (empty($form['answer']['#value'])) {
form_error($form['answer'], t('This field is required.'));
}
if ($form['answer']['#value'] ==
variable_get('total')) {
$msg = t('Good job!');
$type = 'status';
}
else {
$msg = t('Try again...');
$type = 'error';
}
drupal_set_message(check_plain($msg), $type);
}
modified code:
.
.
/**
* Builds the form for configuring Math Questions.
*/
function math_question_page() {
global $user;
$val1 = rand(1,10);
$val2 = rand(1,10);
$total = $val1 + $val2;
$form['math_question'] = array(
'#type' => 'item',
'#markup' => 'What is ' . $val1 . ' + ' . $val2 . ', ' .
check_plain($user->name) . '?',
);
$form['answer'] = array(
'#type' => 'textfield',
'#title' => t('Answer'),
);
$form['total'] = array(
'#type' => 'hidden',
'#value' => $total,
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Check my answer'),
);
return $form;
}
function math_question_page_validate($form, $form_state) {
if (empty($form['answer']['#value'])) {
form_error($form['answer'], t('This field is required.'));
}
if ($form['answer']['#value'] ==
$form['total']['#value']) {
$msg = t('Good job!');
$type = 'status';
}
else {
$msg = t('Try again...');
$type = 'error';
}
drupal_set_message(check_plain($msg), $type);
}

Answer 1

In the validation function math_question_page_validate(), you should access the values from $form_state variable, not from $form.
eg:
if (!$form_state['values']['answer'] == $form_state['values']['total']) {
form_set_error('answer', $error);
}
You can also store the answer in $form_state variable to pass it to the validation function (no need to store the value in $form). if you store it as $form_state['total'], you can access it in the same way (given below).
if (!$form_state['total'] == $form_state['values']['answer']) {form_set_error('answer', $error);}
Thank you very much papirrin for teaching this.
I suggest to use variable_get() to keep the correct answer safe. The random value you keep in the form will not survive the form regeneration.
My working code here.
/**
* Builds the form for configuring Math Questions.
*/
function math_question_page($form, &$form_state) {
global $user;
$val1 = rand(1,10);
$val2 = rand(1,10);
$total = $val1 + $val2;
// Store the correct answer safely away from this form
if (!variable_get('math_question_answer',FALSE)) {
variable_set('math_question_answer', $total);
}
$form['math_question'] = array(
'#type' => 'item',
'#markup' => 'What is ' . $val1 . ' + ' . $val2 . ', ' .
check_plain($user->name) . '?',
);
$form['answer'] = array(
'#type' => 'textfield',
'#title' => t('Answer'),
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Check my answer'),
);
$form_state['redirect'] = FALSE;
return $form;
}
function math_question_page_submit($form, &$form_state) {
if (empty($form['answer']['#value'])) {
form_set_error('answer', t('This field is required.'));
}
else {
if ($form_state['values']['answer'] == variable_get('math_question_answer')) {
$msg = t('Good job!');
$type = 'status';
}
else {
$msg = t('Try again...');
$type = 'error';
}
drupal_set_message(check_plain($msg), $type);
}
variable_del('math_question_answer');
}

Answer 2

Drupal redirects after form submission so your form fields (altogether with your form) are recreated before the validation is called. See details about that in another question.
Your form is created with math_question_page, which does not take any form_state arguments. If you had form_state, then you could detect that math_question_page has not been submitted yet and just keep the state of the last call (last random values).
In order to call math_question_page with a form_state argument, you can use drupal_build_form instead of drupal_get_form in your menu.

Answer 3

Instead of storing the $total in the global variable 'total', try storing it as a hidden field on your form (unless you are worried about your users cheating). You can write:
'#type' => 'hidden,
to create a hidden 'total' field and then check for that value in validate so prevent total to be overwritten.

Answer 4

I am learning to write drupal modules too (Started the tutorial series 2 weeks ago).
I tried to do this same module , and i think that the implementation which saves the random values in the database is NOT correct. The first thing asked in the exercise is this :
Any user visiting the /question path will get a simple add-two-numbers question, such as "What is 4 + 9?".
So acces arguments for the page should be 'access arguments' => array('access content') not 'access arguments' => array('administer_site_configuration').
This comes with the following issue : If there are 2 (or more) users browsing at the same moment this page , the latest user overwrites the values in the database , so the other users won't be able to complete the "question" because his answer will not be equal to the answer in the database. Saving values to database is NOT a option in this case...
Meantime I am trying to make it work without the database , but i have the same situation as this question's starter , the form overwrites the values when i submit it (so , error thrown because the answer is wrong ).
If i'll manage to complete it i'll post the code here , or if someone else managed to complete it without variable_set() and variable_get() , i ask them to post the code here :)