Dessert #1 - The 7 crucials of CRUD

Posted by Felix Geisendörfer, on Sep 14, 2006 - in PHP & CakePHP » Controllers, Components & Shells

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Update: I changed the functions new_one and create to create and save based on Daniel's suggestion in the comments. However I still would love the ability to use new & create but since new can't be used (it's a php keyword), this seems like a good workaround.

When you've worked with CakePHP you might have heard about CRUD before (Create, Read, Update, Delete) which is a pattern used in the database world which translates well into controller actions. Now so usally you would use 5 functions (create, edit, view, delete, + index). And while this isn't a bad idea, you always end up with a couple if statements where you check whether the user already posted some data to Posts::create() or whether he just requests it via GET in order to start writing a new Post.

For that reason, a nice simplification can be achieved by using 7 functions instead of 5. The example below shows you how those additional actions could look like and what should be done inside of them.

php
  1. class PostsController extends AppController
  2. {
  3.     var $name = "Posts";
  4.    
  5.     function index() // GET
  6.     {
  7.         // Prepare the overview of all posts,
  8.         // Usally you'll do something like: $this->set('posts', $this->Post->findAll());
  9.     }
  10.    
  11.     function create() // GET
  12.     {
  13.         // Here goes everything you need to prepare an empty form for you Post
  14.         // to be filled out
  15.        
  16.         // If you don't want to write the template for editing a post twice (for create        
  17.         // and edit), just put a $this->render('edit'); at the end of this function.
  18.     }
  19.    
  20.     function save() // POST
  21.     {
  22.         // This function interacts with your Model ( $this->Posts ) in order to bring
  23.         // $this->data['Post'] into your database
  24.        
  25.         // After it you can call $this->edit($this->Post->getLastInsertID()) in order to
  26.         // display the edit box again if you want the User to continue editing
  27.     }
  28.    
  29.     function show($id) // GET
  30.     {
  31.         // This function shows a Post with a given $id
  32.     }
  33.    
  34.     function edit($id) // GET
  35.     {
  36.         // This function reads the Post with $id from your database and prepares all
  37.         // data for the View to display an edit form for it.
  38.     }
  39.    
  40.     function update() // POST
  41.     {
  42.         // This function takes care of updating the post contained in $this->data['Post']
  43.         // in the database.
  44.        
  45.         // Like with create, you can call $this->edit($this->data['Post']['id']); at the
  46.         // end of this function to let the user continue editing the Post.
  47.     }
  48.    
  49.     function destroy($id) // GET
  50.     {
  51.         // This function destroys the Post a given $id
  52.     }
  53. }

Alright, I might end up posting two desserts today. Since I've been getting up at 5 am every morning I am actually able to post on here before I go to school. Ok, I didn't write something insanly exiting, but it's a start ; ).

--Felix Geisendörfer aka the_undefined

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7 Comments

Christian Tietze on Sep 14, 2006:

So you suggest having a form which redirect the user from /new_one to /create or so? That approach is really nice I think, but nevertheless the method name "new_one" doesn't sound that great in my opinion.
But whatever, it's only an example, so getting the idea is no problem now and it might be useful.

Ben on Sep 14, 2006:

I've always used:

add => create
edit => update
delete => destroy

It makes for code which is easier to read and maintain.

Daniel Hofstetter on Sep 14, 2006:

Your "new_one" function sounds a bit ugly. I would name it "create" and rename the function you named "create" to "save". What do you think about it?

Nate on Sep 14, 2006:

You can actually combine several of those with a simple if (!empty($this->data)) { ...

For example:

function edit ($id) {
if (!empty($this->data)) {
$this->Model->id = $id;
if ($this->Model->save($this->data)) {
// Redirect with flash message
}
} else {
$this->data = $this->Model->read(null, $id);
}
}

could replace edit and update. Likewise for create and new_one.

Brandon Pearce on Sep 14, 2006:

Great post!
To follow up on what Nate said, you could also combine add and edit (or new_one and edit) into the same function like this:

function edit($id=null)
{
if (isset($id))
{
// Get data from model
// render edit
}
else
{
// render add
}
}

Lucian Lature on Sep 14, 2006:

I think Felix already explained why he uses 7 functions instead of 5, he does that to eliminate the if statements. I think this approach is very usefull when it comes to build some API or when you have to create an web wizard.

Felix Geisendörfer on Sep 14, 2006:

Daniel Hofstetter: I think that's a good idea. I went almost nuts this morning trying to find a replacment for "new". This sounds like a reasonable workaround.

Lucian: Yes, that's what I was talking about. The if statements are nice and everything, however, this approach is useful if all those actions use different views since a 1:1 relationship between actions and views takes away some complexity. And of course for things like building API's just like you said.

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