how to create a edit and delete function in a custom module

There are three pieces of code that relate to this. I'll show you how an item is passed to the edit page, and delete page works in the same manner. First, look at my hook_menu() definition for the edit page (I've stripped it down to the relevant lines):

$menu['mycontent/%mycontent/edit'] = array
  (
    // ...
    'page arguments' => array('mymodule_item_form', 1),
    // ...
  );

First is the menu path. You'll notice the %mycontent element of the path. This means that any value can be used in this element, and that value will be passed to the function mycontent_load() (add _load() to the part after the % sign). If I had written it like this:

$menu['mycontent/%/edit'] = array

Then the value in that element of the path would be directly passed to the edit page, without going through the function mycontent_load(). However, my form function is set up to require that an $item is passed to the form function, so I need to load that $item first. This is what happens in mycontent_load().

The next line is here:

 'page arguments' => array('mymodule_item_form', 1),

I am passing two arguments to the callback function drupal_get_form(). The first argument is the name of the function that defines the form, in this case my_module_item_form(). The second argument is an integer, 1. When passing an integer, that index of the menu path is passed to the callback function. Indexes start at zero, so with the above path our indexes are:

0 = mycontent
1 = %mycontent
2 = edit

We want to pass the value from the wildcard, which is why 1 is passed.

The thing to look at is mycontent_load():

function mycontent_load($rid)
{
  return db_query('SELECT rid, my_field FROM {my_table} WHERE rid = :rid', array(':rid' => $rid))->fetchObject();
}

You can see this function receives one argument, $rid. This is the value that was entered into the path. So if someone accesses the path mycontent/3/edit, then the value of $rid would be 3. This value is then used in the db query to load the $item with an $rid of 3.

Note that if a value is not returned here, or if the returned value is false, then the form is never called and the user receives an 'access denied' page (or 'page not found'? I can't remember).

Now that we have generated an $item, it is passed to the form definition here:

function mymodule_item_form($form, &$form_state, $item)

All form definitions (in D7) receive $form, and $form_state. If you pass additional arguments to the function when calling drupal_get_form(), they are also passed to the form definition. Since I passed a loaded $item from the menu path, via mycontent_load(), the form definition receives $item. This is the item to be edited, and you can see I've used it to pass the default value (the value to be edited) to the form element here:

$form['my_field'] = array
  (
    '#title' => t('Enter a value'),
    '#type' => 'textfield',
    '#default_value' => $item->my_field,
  );

If there were more form elements, I would also populate them from the $item object.

This requirement for the $item is why for the item add page, I created an empty $item, then passed it to the form definition here:

function mymodule_add_item_page()
{
  $item = new StdClass;
  $item->rid = FALSE;
  $item->my_field = '';

  return drupal_get_form('mymodule_item_form', $item);
}

You can see I've called drupal_get_form(), passing it the form definition name, mymodule_item_form(), and the empty $item I created.

So to review:

1) The item ID is passed in the URL. Ex: mycontent/5/edit
2) This item ID is used to load an $item in mycontent_load()
3) The $item created in step 2 is passed to the form definition, as is the $item that will be edited.

On an only tangentially related note, since you work with custom entities a lot, are they any faster in general? I'm working on upgrading a site from d6 to d7 and I'm trying to decide if it's worthwhile to redo my content types as custom entities. If I do them as entities, I can lose the field api fields and simply add them directly to the entity. I'm thinking that between shedding field api and the overhead typically incurred with node_load and node_save it could be a performance boost, but I have no data to back that up.

Hi Jaypan,

I have seen your example code that gives a very clear way how to manage custom schema using custom module. I want to implement this example code by Entity API because I need to use this schema inside views also.

code I've given here is essentially the same skeleton I use for my own custom entities. This code can be extended to provide custom entities, by tying into the Entity API with hook_entity_info() and the other relevant hooks.

Can you please share any example or suggestion regarding this, it would help me in correct implementation.

Thanks