Laravel5.1学习笔记22 Eloquent 调整修改

Eloquent: Mutators

• Introduction
• Accessors & Mutators
• Date Mutators
• Attribute Casting

Introduction

Accessors and mutators allow you to format Eloquent attributes when retrieving them from a model or setting their value. For example, you may want to use the Laravel encrypter to encrypt a value while it is stored in the database, and then automatically decrypt the attribute when you access it on an Eloquent model.

In addition to custom accessors and mutators, Eloquent can also automatically cast date fields to Carbon instances or even cast text fields to JSON.

Accessors & Mutators

Defining An Accessor

To define an accessor, create a getFooAttribute method on your model where Foo is the "camel" cased name of the column you wish to access. In this example, we'll defined an accessor for the first_name attribute. The accessor will automatically be called by Eloquent when attempting to retrieve the value of first_name:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * Get the user's first name.
     *
     * @param  string  $value
     * @return string
     */
    public function getFirstNameAttribute($value)
    {
        return ucfirst($value);
    }
}

As you can see, the original value of the column is passed to the accessor, allowing you to manipulate and return the value. To access the value of the mutator, you may simply access the first_name attribute:

$user = App\User::find(1);

$firstName = $user->first_name;

Defining A Mutator

To define a mutator, define a setFooAttribute method on your model where Foo is the "camel" cased name of the column you wish to access. So, again, let's define a mutator for the first_name attribute. This mutator will be automatically called when we attempt to set the value of the first_name attribute on the model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * Set the user's first name.
     *
     * @param  string  $value
     * @return string
     */
    public function setFirstNameAttribute($value)
    {
        $this->attributes['first_name'] = strtolower($value);
    }
}

The mutator will receive the value that is being set on the attribute, allowing you to manipulate the value and set the manipulated value on the Eloquent model's internal$attributes property. So, for example, if we attempt to set the first_name attribute to Sally:

$user = App\User::find(1);

$user->first_name = 'Sally';

In this example, the setFirstNameAttribute function will be called with the value Sally. The mutator will then apply the strtolower function to the name and set its value in the internal $attributes array.

Date Mutators

By default, Eloquent will convert the created_at and updated_at columns to instances ofCarbon, which provides an assortment of helpful methods, and extends the native PHPDateTime class.

You may customize which fields are automatically mutated, and even completely disable this mutation, by overriding the $dates property of your model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * The attributes that should be mutated to dates.
     *
     * @var array
     */
    protected $dates = ['created_at', 'updated_at', 'disabled_at'];
}

When a column is considered a date, you may set its value to a UNIX timestamp, date string (Y-m-d), date-time string, and of course a DateTime / Carbon instance, and the date's value will automatically be correctly stored in your database:

$user = App\User::find(1);

$user->disabled_at = Carbon::now();

$user->save();

As noted above, when retrieving attributes that are listed in your $dates property, they will automatically be cast to Carbon instances, allowing you to use any of Carbon's methods on your attributes:

$user = App\User::find(1);

return $user->disabled_at->getTimestamp();

Attribute Casting

The $casts property on your model provides a convenient method of converting attributes to common data types. The $casts property should be an array where the key is the name of the attribute being cast, while the value is the type you wish to cast to the column to. The supported cast types are: integer, real, float, double, string, boolean,object and array.

For example, let's cast the is_admin attribute, which is stored in our database as an integer (0 or 1) to a boolean value:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * The attributes that should be casted to native types.
     *
     * @var array
     */
    protected $casts = [
        'is_admin' => 'boolean',
    ];
}

Now the is_admin attribute will always be cast to a boolean when you access it, even if the underlying value is stored in the database as an integer:

$user = App\User::find(1);

if ($user->is_admin) {
    //
}

Array Casting

The array cast type is particularly useful when working with columns that are stored as serialized JSON. For example, if your database has a TEXT field type that contains serialized JSON, adding the array cast to that attribute will automatically deserialize the attribute to a PHP array when you access it on your Eloquent model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * The attributes that should be casted to native types.
     *
     * @var array
     */
    protected $casts = [
        'options' => 'array',
    ];
}

Once the cast is defined, you may access the options attribute and it will automatically be deserialized from JSON into a PHP array. When you set the value of the optionsattribute, the given array will automatically be serialized back into JSON for storage:

$user = App\User::find(1);

$options = $user->options;

$options['key'] = 'value';

$user->options = $options;

$user->save();