7.6 KiB
Model
A model in Yii is intended for application data storage and has the following basic features:
- attribute declaration: a model defines what is considered an attribute.
- attribute labels: each attribute may be associated with a label for display purpose.
- massive attribute assignment.
- scenario-based validation.
Models of \yii\base\Model class are typically used to hold data and corresponding validation rules of complex web forms. The class is also a base for more advanced models with additional functionality such as Active Record.
Attributes
Attributes store the actual data represented by a model and can
be accessed like object member variables. For example, a Post model
may contain a title attribute and a content attribute which may be
accessed as follows:
$post->title = 'Hello, world';
$post->content = 'Something interesting is happening';
echo $post->title;
echo $post->content;
Since model implements ArrayAccess interface you can use it as array:
$post['title'] = 'Hello, world';
$post['content'] = 'Something interesting is happening';
echo $post['title'];
echo $post['content'];
Default model implementation has a strict rule that all its attributes should be explicitly declared as public and non-static class properties such as the following:
// LoginForm has two attributes: username and password
class LoginForm extends \yii\base\Model
{
public $username;
public $password;
}
In order to change it you can override attributes() method that returns a list of model attributes. For example,
\yii\db\ActiveRecord class implements attributes as DB table columns:
// Post is associated with the tbl_post DB table.
// Its attributes correspond to the columns in tbl_post
class Post extends \yii\db\ActiveRecord
{
public function table()
{
return 'tbl_post';
}
}
Attribute labels
Attribute labels are mainly used for display purpose. For example, given an attribute firstName, we can declare
a label First Name which is more user-friendly and can be displayed to end users.
By default an attribute label is generated using \yii\base\Model\generateAttributeLabel() but the better way is to specify it explicitly like the following:
// LoginForm has two attributes: username and password
class LoginForm extends \yii\base\Model
{
public $username;
public $password;
public function attributeLabels()
{
reuturn array(
'usename' => 'Your name',
'password' => 'Your password',
);
}
}
Scenarios
A model may be used in different scenarios. For example, a User model may be used to collect user login inputs,
and it may also be used for user registration purpose. For this reason, each model has a property named scenario
which stores the name of the scenario that the model is currently being used in. As we will explain in the next
few sections, the concept of scenario is mainly used in validation and massive attribute assignment.
Associated with each scenario is a list of attributes that are active in that particular scenario. For example,
in the login scenario, only the username and password attributes are active; while in the register scenario,
additional attributes such as email are active.
Possible scenarios should be listed in the scenarios() method which returns an array whose keys are the scenario
names and whose values are the corresponding active attribute lists. Below is an example:
class User extends \yii\db\ActiveRecord
{
public function scenarios()
{
return array(
'login' => array('username', 'password'),
'register' => array('username', 'email', 'password'),
);
}
}
Sometimes, we want to mark that an attribute is not safe for massive assignment (but we still want it to be validated).
We may do so by prefixing an exclamation character to the attribute name when declaring it in scenarios(). For example,
array('username', 'password', '!secret')
Validation
When a model is used to collect user input data via its attributes, it usually needs to validate the affected attributes to make sure they satisfy certain requirements, such as an attribute cannot be empty, an attribute must contain letters only, etc. If errors are found in validation, they may be presented to the user to help him fix the errors. The following example shows how the validation is performed:
$model = new LoginForm;
$model->username = $_POST['username'];
$model->password = $_POST['password'];
if ($model->validate()) {
// ...login the user...
} else {
$errors = $model->getErrors();
// ...display the errors to the end user...
}
The possible validation rules for a model should be listed in its rules() method. Each validation rule applies to one
or several attributes and is effective in one or several scenarios. A rule can be specified using a validator object - an
instance of a \yii\validators\Validator child class, or an array with the following format:
array(
'attribute1, attribute2, ...',
'validator class or alias',
// specifies in which scenario(s) this rule is active.
// if not given, it means it is active in all scenarios
'on' => 'scenario1, scenario2, ...',
// the following name-value pairs will be used
// to initialize the validator properties...
'name1' => 'value1',
'name2' => 'value2',
....
)
When validate() is called, the actual validation rules executed are determined using both of the following criteria:
- the rules must be associated with at least one active attribute;
- the rules must be active for the current scenario.
Active Attributes
An attribute is active if it is subject to some validations in the current scenario.
Safe Attributes
An attribute is safe if it can be massively assigned in the current scenario.
Massive Attribute Retrieval and Assignment
Attributes can be massively retrieved via the attributes property.
The following code will return all attributes in the $post model
as an array of name-value pairs.
$attributes = $post->attributes;
var_dump($attributes);
Using the same attributes property you can massively assign data from associative array to model attributes:
$attributes = array(
'title' => 'Model attributes',
'create_time' => time(),
);
$post->attributes = $attributes;
In the code above we're assigning corresponding data to model fields named as array keys. The key difference from mass retrieval that always works for all attributes is that in order to be assigned an attribute should be safe else it will be ignored.
Validation rules and mass assignment
In Yii2 unlike Yii 1.x validation rules are separated from mass assignment. Validation
rules are described in rules() method of the model while what's safe for mass
assignment is described in scenarios method:
function rules()
{
return array(
// rule applied when corresponding field is "safe"
array('username', 'length', 'min' => 2),
array('first_name', 'length', 'min' => 2),
array('password', 'required'),
// rule applied when scenario is "signup" no matter if field is "safe" or not
array('hashcode', 'check', 'on' => 'signup'),
);
}
function scenarios()
{
return array(
// on signup allow mass assignment of username
'signup' => array('username', 'password'),
'update' => array('username', 'first_name'),
);
}
Note that everything is unsafe by default and you can't make field "safe" without specifying scenario.