Yii2: How to set default attribute values in ActiveRecord?

Question

This may seem like a trivial question, however all of the obvious solutions that I can think of have their own flaws.

What we want is to be able to set any default ActiveRecord attribute value for new records only, in a way that makes it readable before and during validation and does not interfere with derived classes used for search.

The default values need to be set and ready as soon as we instantiate the class, so that (new MyModel)->attr returns the default attr value.

Here are some of the possibilities and the problems they have:

A) In MyModel override the init() method and assign default value when isNewRecord is true like so:
```
public function init() {
    if ($this->isNewRecord) {
        $this->attr = 'defaultValue';
    }
    parent::init();
}
```
Problem: Search. Unless we explicitly unset our default attribute in MySearchModel (very error-prone because it is too easy to forget), this will also set the value before calling search() in the derived MySearchModel class and interfere with searching (the attr attribute will already be set so search will be returning incorrect results). In Yii1.1 this was resolved by calling unsetAttributes() before calling search(), however no such method exists in Yii2.
B) In MyModel override the beforeSave() method like so:
```
public function beforeSave($insert) {
    if ($insert) {
        $this->attr = 'defaultValue';
    }
    return parent::beforeSave();
}
```
Problem: Attribute is not set in unsaved records. (new MyModel)->attr is null. Worse yet, even other validation rules that rely on this value will not be able to access it, because beforeSave() is called after validation.
C) To ensure the value is available during validation we can instead override the beforeValidate() method and set the default values there like so:
```
public function beforeValidate() {
    if ($this->isNewRecord) {
        $this->attr = 'defaultValue';
    }
    return parent::beforeValidate();
}
```
Problem: Attribute is still not set in unsaved (unvalidated) records. We need to at least call $model->validate() if we want to get the default value.

D) Use DefaultValidator in rules() to set a default attribute value during validation like so:

public function rules() {
    return [
        [
            'attr', 'default',
            'value' => 'defaultValue',
            'on' => 'insert', // instantiate model with this scenario
        ],
        // ...
    ];
}

Problem: Same as B) and C). Value is not set until we actually save or validate the record.

So what is the right way to set default attribute values? Is there any other way without the outlined problems?

$model = new DatabaseTable(); that's all you need, $model now has all the default attributes from the database table — Coz
– Coz, Commented Jan 18, 2017 at 3:36
@Coz Nope, that won't work for any dynamic attributes such as the current user's ID. — mae
– mae, Commented Jan 18, 2017 at 4:31
Yeah it will, just use a custom callback. That said though if you want the current users id then use yiiframework.com/doc-2.0/yii-behaviors-blameablebehavior.html instead. — Coz
– Coz, Commented Jan 18, 2017 at 16:18
As you probably found out by yourself, behaviors, including the one you linked, only set the default value before inserting or updating the record. They are not the right answer as we need the value much earlier - on initialization (see option B). — mae
– mae, Commented Jan 19, 2017 at 5:47
Description of the DefaultValidator said that it is not actual validatior. So if your create rule for default values you also should remove these fields from required rule! After that model will contain default values before validation/save calls. — Pavel Sokolov
– Pavel Sokolov, Commented May 11, 2019 at 20:00

Coz · Accepted Answer · 2017-01-18 03:45:30Z

29

There's two ways to do this.

$model => new Model();

Now $model has all the default attributes from the database table.

Or in your rules you can use:

[['field_name'], 'default', 'value'=> $defaultValue],

Now $model will always be created with the default values you specified.

You can see a full list of core validators here http://www.yiiframework.com/doc-2.0/guide-tutorial-core-validators.html

answered Jan 18, 2017 at 3:45

Coz

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2 Comments

mae Over a year ago

As I pointed out in option D, this solution is insufficient, because the value is not actually set until $model->validate() is executed.

antoniom Over a year ago

Regarding your first part of the question, you need to invoke $model->loadDefaultValues() for getting default attributes from the database table yiiframework.com/doc/guide/2.0/en/…. Please consider updating your answer

Arth · Accepted Answer · 2019-03-14 00:50:11Z

19

This is a hangup with Yii's bloated multi-purpose ActiveRecords

In my humble opinion the form models, active records, and search models would be better off split into separate classes/subclasses

Why not split your search models and form models?

abstract class Creature extends ActiveRecord {
    ...
}

class CreatureForm extends Creature {

    public function init() {
        parent::init();
        if ($this->isNewRecord) {
            $this->number_of_legs = 4;
        }
    }
}

class CreatureSearch extends Creature {

    public function search() {
        ...
    }
}

The benefits of this approach are

You can easily cater for different validation, set up and display cases without resorting to a bunch of ifs and switches
You can still keep common code in the parent class to avoid repetition
You can make changes to each subclass without worrying about how it will affect the other
The individual classes don't need to know about the existence of any of their siblings/children to function correctly

In fact, in our most recent project, we are using search models that don't extend from the related ActiveRecord at all

edited Mar 14, 2019 at 0:50

answered Mar 13, 2019 at 17:02

Arth

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4 Comments

mae Over a year ago

It's an old question. This is almost exactly how I've been doing it since. Should be documented like this in Yii.

Anton Rybalko Over a year ago

Bad solution. Search model would have default values - grid view would be filtered by default with default values.

Arth Over a year ago

@AntonRybalko I don't understand your comment.. the default values are set in CreatureForm (used to manipulate records) and NOT set in CreatureSearch (used for the GridView). So the GridView would NOT be filtered by default with default values.

Anton Rybalko Over a year ago

Oops, sorry. Didn't notice it.

mae · Accepted Answer · 2017-08-11 06:58:39Z

7

I know it is answered but I will add my approach. I have Application and ApplicationSearch models. In Application model I add init with a check of the current instance. If its ApplicationSearch I skip initializations.

    public function init()
    { 
        if(!$this instanceof ApplicationSearch)  
        {
            $this->id = hash('sha256',  123);
        }

        parent::init();
    }

also as @mae commented below you can check for existence of search method in current instance, assuming you didn't add any method with name search to the non-search base model so the code becomes:

    public function init()
    { 
        // no search method is available in Gii generated Non search class
        if(!method_exists($this,'search'))  
        {
            $this->id = hash('sha256',  123);
        }

        parent::init();
    }

edited Aug 11, 2017 at 6:58

mae

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answered Dec 19, 2016 at 10:14

Stefano Mtangoo

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4 Comments

mae Over a year ago

I like this best and it gave me an even better idea. Check for !method_exists($this,'search') instead so you don't have to know the child class name.

Arth Over a year ago

I'm sorry, I really don't like this approach.. you are introducing a dependency on the child class from the parent. The child should be able to be changed willy-nilly without affecting the functionality of the parent, and any functionality specific to the child should be visible in the child. Checking for a method named 'search' is even worse!

Stefano Mtangoo Over a year ago

@Arth, given the question constraints what is your proposed solution?

Arth Over a year ago

I have added an answer

Bizley · Accepted Answer · 2016-09-04 08:00:57Z

3

I've read your question several times and I think there are some contradictions.
You want the defaults to be readable before and during validation and then you try init() or beforeSave(). So, assuming you just want to set the default values in the model so they can be present during the part of the life cycle as long as possible and not interfere with the derived classes, simply set them after initialising the object.

You can prepare separate method where all defaults are set and call it explicitly.

$model = new Model;
$model->setDefaultValues();

Or you can create static method to create model with all default values set and return the instance of it.

$model = Model::createNew();

Or you can pass default values to constructor.

$model = new Model([
    'attribute1' => 'value1',
    'attribute2' => 'value2',
]);

This is not much different from setting the attributes directly.

$model = new Model;
$model->attribute1 = 'value1';
$model->attribute2 = 'value2';

Everything depends on how much transparent would you like your model be to your controller.

This way attributes are set for the whole life cycle except the direct initialisation and it's not interfering with derived search model.

answered Sep 4, 2016 at 8:00

Bizley

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11 Comments

meysam Over a year ago

It's good to use Yii::createObject instead of new keyword.

Bizley Over a year ago

Why? new is so much faster.

meysam Over a year ago

Yii::createObject lets you do more than new. Also in my opinion it saves the semantic schema of Yii2. Other users can gain more understanding from you code, because all initializations are in one place, neither in different places nor different methods.

Bizley Over a year ago

It's true, it's for DI container but in here it is overkill for such a simple case. Yii 2 core is not using this in every case as well - it affects performance.

mae Over a year ago

You understood my question correctly, but unfortunately the solutions you propose just aren't usable in the real world. The statement (new MyModel)->attr needs to return the default attr value. The whole point of default attribute values is that we don't have to manually set them every time.

|

Игорь Чугусов · Accepted Answer · 2018-05-12 21:57:03Z

2

Just override __construct() method in your model like this:

class MyModel extends \yii\db\ActiveRecord {

    function __construct(array $config = [])
       {
           parent::__construct($config);
           $this->attr = 'defaultValue';
       }
    ...
}

answered May 12, 2018 at 21:57

Игорь Чугусов

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1 Comment

mae Over a year ago

This also breaks search models (see scenario A).

Dedy Kurniawan · Accepted Answer · 2021-06-11 02:34:06Z

1

If you want to load default value from database you can put this code in your model

 public function init()
 {
    parent::init(); 
    if(!method_exists($this,'search')) //for checking this code is on model search or not
    {
        $this->loadDefaultValues();
    }
 }

answered Jun 11, 2021 at 2:34

Dedy Kurniawan

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Comments

user6606668 · Accepted Answer · 2017-02-08 06:25:52Z

-1

You can prepare separate method where all defaults are set and call it explicitly.

$model = new Model;
if($model->isNewRecord())
    $model->setDefaultValues();

answered Feb 8, 2017 at 6:25

user6606668

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