What are some of the ways you have implemented models in the Zend Framework?
I have seen the basic class User extends Zend_Db_Table_Abstract and then putting calls to that in your controllers:
$foo = new User;
$foo->fetchAll()
but what about more sophisticated uses? The Quickstart section of the documentation offers such an example but I still feel like I'm not getting a "best use" example for models in Zend Framework. Any interesting implementations out there?
EDIT: I should clarify (in response to CMS's comment)... I know about doing more complicated selects. I was interested in overall approaches to the Model concept and concrete examples of how others have implemented them (basically, the stuff the manual leaves out and the stuff that basic how-to's gloss over)
I worked for Zend and did quite a bit of work on the Zend_Db_Table component.
Zend Framework doesn't give a lot of guidance on the concept of a "Model" with respect to the Domain Model pattern. There's no base class for a Model because the Model encapsulates some part of business logic specific to your application. I wrote a blog about this subject in more detail.
Persistence to a database should be an internal implementation detail of a Model. The Model typically uses one or more Table. It's a common but improper object-oriented design to consider a Model as an extension of a Table. In other words, we should say Model HAS-A Table -- not Model IS-A Table.
This is an example of IS-A:
class MyModel extends Zend_Db_Table_Abstract
{
}
This is an example of HAS-A:
class MyModel // extends nothing
{
protected $some_table;
}
In a real domain model, you would use $some_table in the methods of MyModel.
You can also read Martin Fowler's take on the Domain Model design pattern, and his description of the Anemic Domain Model antipattern, which is how many developers unfortunately approach OO programming.
I personally subclass both Zend_Db_Table_Abstract and Zend_Db_Table_Row_Abstract. The main difference between my code and yours is that explicitly treat the subclass of Zend_Db_Table_Abstract as a "table" and Zend_Db_Table_Row_Abstract as "row". Very rarely do I see direct calls to select objects, SQL, or the built in ZF database methods in my controllers. I try to hide the logic of requesting specific records to calls for behind Zend_Db_Table_Abstract like so:
class Users extends Zend_Db_Table_Abstract {
protected $_name = 'users';
protected $_rowClass = 'User'; // <== THIS IS REALLY HELPFUL
public function getById($id) {
// RETURNS ONE INSTANCE OF 'User'
}
public function getActiveUsers() {
// RETURNS MULTIPLE 'User' OBJECTS
}
}
class User extends Zend_Db_Table_Row_Abstract {
public function setPassword() {
// SET THE PASSWORD FOR A SINGLE ROW
}
}
/* CONTROLLER */
public function setPasswordAction() {
/* GET YOUR PARAMS */
$users = new Users();
$user = $users->getById($id);
$user->setPassword($password);
$user->save();
}
There are numerous ways to approach this. Don't think this is the only one, but I try to follow the intent of the ZF's design. (Here are more of my thoughts and links on the subject.) This approach does get a little class heavy, but I feel it keeps the controllers focused on handling input and coordinating with the view; leaving the model to do the application specific work.
Don't ever use Zend_Db_Table as your model. It just gets you into trouble. Either you write your own model classes which use Zend_Db_Table to talk to your database or you can read my blog post here for a hack that allows you to somewhat combine the "Model" class and Zend_Db_Table.
The main thing to not is that when you use Zend_Db_Table directly in your controllers you end up doing the same things in multiple places. If you have to make a change to some of that logic, you have to make a change in multiple places. Not good. My first professional project was done like this because I was the one in the company who had to learn how to use ZF and it's a total mess now.
I also tend to write helper functions into my classes for sophisticated fetches. Somthing like $table->doNameFetchAll() or $table->doOrderFetchAll().
I've been doing some research on Models for ZF and came across an interesting series of articles by Matthew Weier O'Phinney which are well worth checking out:
Using Zend_Form in your Models
Applying ACLs to Models
Model Infrastructure
It's not "production code" and a lot is left to the imagination, but it's a good read and has helped me quite a bit.
A model has nothing to do with the database. What if I am fetching data from an RSS feed or a SOAP service or reading files from the FS?
I put all these kinds of things in models. In that case, my model class might not extend anything. I'm about to write a model that uses methods of other models.
Skip ZF for the models part, there are much better solutions. The "M" in ZF's "MVC" is pretty much absent. Reading their docs they don't really mention models at all -- which is a good thing, it means you can use just about anything you want without writing lots of adapter code.
Take a look at Doctrine for models instead. It is quickly becoming the de-facto ORM for PHP.
You can do more complicated queries, check the Advanced usage section in the Zend_Db_Table manual page.
$select = $table->select();
$select->from($table,
array('COUNT(reported_by) as `count`', 'reported_by'))
->where('bug_status = ?', 'NEW')
->group('reported_by');
you can extend the Zend_Db_Table_Abstract class and add some useful methods to it. for example you can add a changePassword() method to your user class and manipulate it's data. or you can change the default __toString() method of your class, so you'll have a customized __toString() method that, let's say returns the whole contact information of the user (name, address, phone number) in a well formatted string. in your constructor you could populate your data into properties of your object. then use them like:
public function __toString() {
$data = $this->_name . ', ' . $this->_adderss . ', call: ' . $this->_phone;
return $data;
}
your model extends the Zend_Db_Table_Abstract just to ease the process of accessing its data, but the functionality you could have on that data is all up on your creativity and need.
I recommend you the book "php|architect's guide to programming with zend framework" by Cal Evans. the book is very informative and easy to read. chapters 4 and 6 are going to be useful for this matter.
A database entity is not the only kind of model component. As such, it doesn't really make sense to speak of models (in plural) - Your application has one model, which contains a multitude of components. Some of these components could be table gateways (And thus extend from Zend_Db), while others would not.
I recommend that you get hold of the book Domain Driven Design by Eric Evans, which does an excellent job of explaining how to construct an object model.
I use Propel 1.3 instead of Zend_Db_Table.
It's tricky to setup, but awesome.
It can examine your database and auto-generate all your models.
It actually generates 2 levels and 2 types of model.
Examples for 'user' table:
Level 1: BaseModel & BasePeer: these get overwritten every time you regenerate your ORM. i.e. BaseUser.php & BaseUserPeer.php
Level 2: StubModel & StubPeer: these don't get overwritten. They're the ones you customize. i.e. User.php & UserPeer.php
Type 1: Model - for basic CRUD operations, not queries i.e. User.php
Type 2: Peer -- for queries. These are static objects. i.e. UserPeer.php
So to create a user:
$derek = new User();
$derek->setFirstName('Derek');
$derek->save();
To find all dereks:
$c = new Criteria();
$c->add(UserPeer::FIRST_NAME, 'Derek');
$dereks = UserPeer::doSelect($c);
http://zfsite.andreinikolov.com/2008/08/zend_db_table-time-overhead-about-25-percents/
Bit of a catch 22, Zend_Table is nice in principle, but generates some performance overheads (without caching)...
Related
I've been looking at Laravel for awhile and I decided to finally pick it up. It's my first time using a PHP framework and I'm having some trouble grasping the purpose of the models.
I've been reading a lot of newbie guides and this is pretty much all that is in their model (Laravel wise),
class Model extends Eloquent {
}
And then in their controller they do something like this,
$model = new Model;
$model->text = "text";
$model->save();
I'm no expert at the MVC pattern (probably the biggest newbie out there) but I thought the whole point (or at least a small point) was to separate a lot of actions. And that the model was supposed to be responsible of handling everything DB-wise. So in a way, this seems wrong to me or at least not the best practice.
But if you start setting up a bunch of functions you could run into the issue of having one model for every table. Which again, doesn't seem right. So you have to make the model, in a way, ambiguous. In the sense that it can take any actions against any table?
It all just seems really confusing to me at the moment.
You are going to need a model for evey table, because there are other things related to models that cannot be shared, like column names and validation, but if you think you are repeating yourself, you can create a BaseModel and add all methods or even overload Eloquent methods in it:
class BaseModel extends Eloquent {
public function whatever() {
}
public function save(array $options = []) {
// do what you need to do
parent::save();
}
}
Then create your models using it:
class Order extends BaseModel {
}
But you don't need much on a model, if your models and tables names follows Laravel pattern (in this case the table name would be 'orders'), then you just need this simple declaration to have a model working for your table.
Edit:
Controllers are meant to transfer data from a model to a view, but they should not know too much about your data, almost everything about them should lies in your models ("Fat models, skinny controllers"), so they need to know just enough to have "control".
class OrdersController extends BaseController {
public function process()
{
$order = Order::find( Input::get('orderId') )->process();
return View::make('orders.showProcessedOrder')->with('order',$order);
}
}
Models are a wrapper around your database tables. Your database tables are the real-world things you are making your application about. Models allow you to use your programming language for CRUD'ing (creating, reading, updating or deleting) data. OOP is all about classes and objects, and converting things like incoming HTTP requests and data storage into that form.
Your question is a good one. When you learn how to make Web applications, having a three-tiered web app - a presentation layer, a business-logic layer and data-storage layer with data stored in a relational database - works great, and it makes no doggone sense to add an extra layer of database-related stuff in the code.
And, like Antonio wrote, in MVC programming, "fat models, skinny controllers" is what you're working towards. The controller ideally should just be a couple of lines of code that pass the incoming request to the correct model where it could be validated, added to the database, etc. (But it is easiest to put that in the controller while you're first learning/figuring MVC out.)
I'm seriously confused about the concept of the 'Model' in MVC. Most frameworks that exist today put the Model between the Controller and the database, and the Model almost acts like a database abstraction layer. The concept of 'Fat Model Skinny Controller' is lost as the Controller starts doing more and more logic.
In DDD, there is also the concept of a Domain Entity, which has a unique identity to it. As I understand it, a user is a good example of an Entity (unique userid, for instance). The Entity has a life-cycle -- it's values can change throughout the course of the action -- and then it's saved or discarded.
The Entity I describe above is what I thought Model was supposed to be in MVC? How off-base am I?
To clutter things more, you throw in other patterns, such as the Repository pattern (maybe putting a Service in there). It's pretty clear how the Repository would interact with an Entity -- how does it with a Model?
Controllers can have multiple Models, which makes it seem like a Model is less a "database table" than it is a unique Entity.
UPDATE: In this post the Model is described as something with knowledge, and it can be singular or a collection of objects. So it's sound more like an Entity and a Model are more or less the same. The Model is an all encompassing term, where an Entity is more specific. A Value Object would be a Model as well. At least in terms of MVC. Maybe???
So, in very rough terms, which is better?
No "Model" really ...
class MyController {
public function index() {
$repo = new PostRepository();
$posts = $repo->findAllByDateRange('within 30 days');
foreach($posts as $post) {
echo $post->Author;
}
}
}
Or this, which has a Model as the DAO?
class MyController {
public function index() {
$model = new PostModel();
// maybe this returns a PostRepository?
$posts = $model->findAllByDateRange('within 30 days');
while($posts->getNext()) {
echo $posts->Post->Author;
}
}
}
Both those examples didn't even do what I was describing above. I'm clearly lost. Any input?
Entity
Entity means an object that is a single item that the business logic works with, more specifically those which have an identity of some sort.
Thus, many people refer to ORM-mapped objects as entities.
Some refer to as "entity" to a class an instance of which represents a single row in a database.
Some other people prefer to call only those of these classes as "entity" which also contain business rules, validation, and general behaviour, and they call the others as "data transfer objects".
Model
A Model is something that is not directly related to the UI (=View) and control flow (=Controller) of an application, but rather about the way how data access and the main data abstraction of the application works.
Basically, anything can be a model that fits the above.
MVC
You can use entities as your models in MVC. They mean two different things, but the same classes can be called both.
Examples
A Customer class is very much an entity (usually), and you also use it as part of data access in your app. It is both an entity and a model in this case.
A Repository class may be part of the Model, but it is clearly not an entity.
If there is a class that you use in the middle of your business logic layer but don't expose to the rest of the application, it may be an entity, but it is clearly not a Model from the perspective of the MVC app.
Your example
As for your code examples, I would prefer the first one.
A Model is a class that is used as a means of data abstaction of an application, not a class which has a name suffixed with "Model". Many people consider the latter bloatware.
You can pretty much consider your Repository class as part of your model, even if its name isn't suffixed with "Model".
I would add to that the fact that it is also easier to work with the first one, and for other people who later may have to understand your code, it is easier to understand.
All answers are a heavy mashup of different things and simply wrong.
A model in DDD is much like a model in the real world:
A simplification and abstraction of something.
No less and no more.
It has nothing to do with data nor objects or anything else.
It's simply the concept of a domain part. And in also every complex domain
there is always more than one model, e.g. Trading, Invoicing, Logistics.
An entity is not a "model with identity" but simply an object with identity.
A repository is not just a 1st level cache but a part of the domain too.
It is giving an illusion of in-memory objects and responsible for fetching
Aggregates (not entities!) from anywhere and saving them
i.e. maintaining the life cycle of objects.
The "model" in your application is the bit which holds your data. The "entity" in domain-driven design is, if I remember correctly, a model with an identity. That is to say, an entity is a model which usually corresponds directly to a "physical" element in a database or file. I believe DDD defines two types of models, one being the entity, the other being the value, which is just a model without and identity.
The Repository pattern is just a type of indexed collection of models/entities. So for instance if your code wants order #13, it will first ask the repository for it, and if it can't get it from there, it will go and fetch it from wherever. It's basically a level 1 cache if you will. There is no difference in how it acts with a model, and how it acts with an entity, but since the idea of a repository is to be able to fetch models using their IDs, in terms of DDD, only entities would be allowed into the repository.
A simple solution using service and collection:
<?php
class MyController {
public function index() {
$postService = ServiceContainer::get('Post');
$postCollection = $postService->findAllByDateRange('within 30 days');
while($postCollection->getNext()) {
echo $postCollection->current()->getAuthor();
}
}
}
EDIT:
The model(class) is the simple representation of the entity scheme. The model(object) is a single entity. The service operates on models and provides concrete data to the controllers. No controller has any model. The models stand alone.
On the other "side", mappers map the models into persistance layers (e.g: databases, 3rd party backends, etc).
while this is specifically about Ruby on Rails, the same principles and information still apply since the discussion is around MVC and DDD.
http://blog.scottbellware.com/2010/06/no-domain-driven-design-in-rails.html
In the Zend Framework Quickstart, there has been a change from models that extend Zend_Db_Table_Abstract to the Table Data Gateway pattern.
Personally, I have not had much experience with this pattern and I keep hearing this should most likely be used instead of the old way.
A short example from the quickstart:
Old way:
class Default_Model_Guestbook extends Zend_Db_Table_Abstract
{
protected $_name = 'tablename';
// do stuff
}
New way:
// The actual model
class Default_Model_Guestbook
{
protected $_comment;
protected $_created;
protected $_poster;
// list continues with all columns
}
// Dbtable for this model
class Default_Model_DbTable_Guestbook extends Zend_Db_Table_Abstract
{
/** Table name */
protected $_name = 'guestbook';
}
// Mapper
class Default_Model_GuestbookMapper
{
public function save($model);
public function find($id, $model);
public function fetchAll();
}
From my lacking experience with this style of programming, I find it hard to grasp the actual benefits from this latter way; I understand that this method seperates the database from the actual logic as much as possible, which should in theory make a transition to another database platform easier. However, I really don't see this happening on any project I am working.
There is almost no doubt that I am overlooking something, so I'd love to hear your advice.
The question:
Could someone please explain to me why (or if) the latter is better practice?
Should I switch from the old way to the new way or are there still proper reasons for sticking with models that represent database tables?
Thanks in advance.
Here's my explanation at why this is a better practice:
I think the real benefit to this is the ability to seamlessly change your data sources. By adding an additional layer of abstraction into your application, your models no longer represent a database table (it never should have, in my opinion) as a model should be a representation of the data (not a gateway to it). The database access layer should be encapsulated by the model, allowing you more flexibility.
Say, for instance, your application needed to start using a SOAP service or XML-RPC as it's data source/storage. By using the data mapper approach, you are at a distinct advantage, as you already have the necessary structure in place to add these specific data layer interfaces without much (if any) interference with your existing models.
Should you do it, though? That's a pragmatic question. Personally, I like to have the peace of mind that I'm developing something that is flexible and follows (agreed on) best practices. However, only you know whether creating a more flexible application will make your projects easier, either now or some time in the future, to build and maintain.
For me, I just like the feeling that I'm building something, I consider to be best-practice and it often pays dividends.
It's useful because you can do $insert = new Model_Guestbook($param1, $param2, $param3); - means when someone comes to the project, he can create a new instance easily without knowledge of the database structure (by checking the source / by model interface). This is just one of the benefits this method offers :)
Now I have an model User which represents an user in the application. And I use an UserRepository with methods like getById($id) and getAll().
An user can post reviews. If I want to show the 5 or 10 or maybe 20 last reviews of an user it's most logical to ask the user I think. So I would have a method $user->getLastReviews(5).
But what's the best way to implement this? Give each user an instance of the ReviewRepository (with a method $reviewRepository->getByUser(User $user) for example)? Or are there better ways?
I think it's fine to have models contain and use instances of other models, so your way is fine, to have User model contain an instance of the Review model, and let that Review model handle the logic of getting said reviews.
Also, you could add a method to the UserRepository to handle it like so:
class UserRepository extends Model{
$review = new reviewRepository();
function getReviews($numOfReviews){
return $this->review->getReviews($user_id);
}
Another option would be to create a repository method where you passed in both variables. Something like $reviewRepository->getLastReviewsByUser(5, $user).
Usually this is a job for the ORM. Almost every framework uses one implementation (ie. Doctrine for PHP/Symfony or Hibernate for Java) but naturally you can implement your own ORM (ORM are often implemented using introspection).
Once you have an ORM library you define relations between Models in a "setup phase" (in your case you'll have "user has many reviews"). Then you'll use the ORM methods which knows how to deal with those ones (often relations are mutual ie. "review belongs to user"). The concept is that this setup phase will discharge you from dealing with issues like the one you pointed.
My suggestion is to use one of the already existing ORM implementations which already supplies facilities for getter and setter methods of related Models. In the other case, you have to write specialized getters and setters by yourself for every Model.
It used to be that within a CodeIgniter model you couldn't access another model.
$this->load->model('bar');
$this->bar->something();
Is this still valid, or have they changed it?
Those are some VERY long answers for a simple question.
Short answer: This is now fully supported. Cross-load away if you feel like it!
I strongly disagree with the notion that a "model" should only encapsulate a database table with simple CRUD operations. As noted in the Wikipedia article:
http://en.wikipedia.org/wiki/Model-view-controller#As_a_design_pattern
...that application layer is intended to do more than simply act as a single database table abstraction. Think about the meaning of the word "controller" -- it should act more as a director rather than being the entire application in and of itself. A "model" is a place for business logic. Most large scale applications in fact hold much of their business logic in the database itself (in the form of triggers, stored procedures, foreign keys, etc.).
I think the misunderstanding of what a "model" is is partly caused by the same (over-)hype of "MVC", without carrying with it much understanding of the concepts themselves. Kinda like how empty "AJAX" is, or even more easy, "Web 2.0". For better or worse, plenty of script kiddies have jumped on the MVC wagon, and since the simple howtos and example scenarios don't do much more than tell you to put your database code in the "model", the misuse of that layer as only a database abstraction has become commonplace. Now you read posts all over the Internet calling it "unpure", "dirty", "hackish" to put any business logic in a model. That's WRONG. Misinformed.
The easy example is to think about foreign keys: even if you only want your "model" to be a database model, if you want to be "pure", "correct" or what have you, you really should be enforcing referential integrity therein. Thanks to the lack of real foreign key support in MySQL for many years, web applications grew up without anyone worrying about referential integrity at all. Fits the script kiddie lifestyle I guess. Anyhow, for even this simplified view of a model to be able to maintain foreign key validity, a model then has to work with others (or, especially if a framework like CodeIgniter does not let you do so, you have to write queries to other tables, sometimes duplicating queries elsewhere - THAT is bad style).
Therefore, I believe this to be a shortcoming of CodeIgniter. I understand that it might not be an easy fix, but it's certainly a disappointing oversight.
So what I did was take the example code above and abstract it into a helper so that I now have a function that works almost identically to the normal $this->load->model() functionality. Here it is (put it into a helper that is auto-loaded and you can use it in any model):
/**
*
* Allow models to use other models
*
* This is a substitute for the inability to load models
* inside of other models in CodeIgniter. Call it like
* this:
*
* $salaries = model_load_model('salary');
* ...
* $salary = $salaries->get_salary($employee_id);
*
* #param string $model_name The name of the model that is to be loaded
*
* #return object The requested model object
*
*/
function model_load_model($model_name)
{
$CI =& get_instance();
$CI->load->model($model_name);
return $CI->$model_name;
}
It's possible, but not ideal and considered bad and more for "quick fix" than ideal or pure implementation.
class Location extends Model{
public function get($ID){
// Get main CI object handle and load model
$CI =& get_instance();
$CI->load->model('LocationType');
// Call new model functions using handle to main CI object
$CI->LocationType->setID($result->LocationTypeID);
$CI->LocationType->setTitle($result->TypeTitle);
$this->_locationType = $CI->LocationType;
//Other Stuff
}
}
Anytime you're using the main CI object like this is probably a bad idea. Try to re-think your layout and just pass data to/from your controller to the models.
http://codeigniter.com/forums/viewthread/69833/
You can load models from models as Phil Sturgeon says, but you have to be careful of dependencies if you load the models in the model constructor: if model A uses model B and model B uses model A, when you try to load one or the other, you'll go into an infinite loop.
In situations like this in Code Igniter I prefer one of two posiibilities:
1) Have model's attribute and setter like this:
class X extends Model {
var $Y_model;
public function setY($Y) {
$this->Y_model = $Y;
}
public function doItRightNow($a,$b) {
$list = $this->Y_model->getSomeList($a,$b);
// ...
}
// ...
}
And then use this setter before other methods to give an instance of other model so it can be used by methods.
$this->load->model('X');
$this->load->model('Y');
$this->X->setY($this->Y);
$this->X->doItRightNow($something,$somethingElse);
2) To have a parameter in method by which I will give an other model instance from controller.
class X extends Model {
public function doItRightNow($a,$b,$Y_model) {
$list = $Y_model->getSomeList($a,$b);
// ...
}
// ...
}
And use it like this:
$this->load->model('X');
$this->load->model('Y');
$this->X->doItRightNow($something,$somethingElse,$this->Y);
I think that these are more clean possibilities.
Which way to use depends on how many methods need to access other model. If there are one or two it might be better to give it as a method parameter. If more - I think it's better to have a class attribute and setter.
And in elegant way you can give one model or another depending on some condition - if they both partially implement same interface with the same kind of data returned (it's rarely useful, but it can be sometimes).
I think it's generally better the write libraries that access the models and then include the libraries in your model if need be.
For instance, if you needed to check if someone is authorized to go through with a certain CRUD action, you might want to include whatever authentication library you are using (its probably auto-included in most cases). You wouldn't necessarily want to access the model directly--it just seems dirty and improper.
I think the preferred way is to do what you need to do in your controller and pass the results from one model's method(s), if need be, to your other model's method(s).
Regardless, I can't see why it wouldn't be possible to include one model into another, per se. I don't think you can do it with the syntax you are showing, though. You would have to do it some other convoluted way. In any case, IMO, it's bad practice to include a model directly into another model.
In CI 2.0 you can just call one model directly from another.
Better to create a helper function instead of calling the function from another model so that it can be used in 2 models at a time and code can be reused.