Transformer

Transform raw input data into consistent, immutable data transfer objects.

Getting Started

Run the following to add Transfromer to your project's composer.json. See Packagist for specific versions.

composer require deefour/transformer

>=PHP5.5.0 is required.

Overview

• All transformers extend the abstract Deefour\Transformer\Transformer class.
• A tranformer accepts a single array of data during instantiation.
• Attributes on the input source can be cast into specific types.
• A getter can be created for each attribute to define a transformation of it's raw value.
• Methods can be created to provide additional, custom attributes.
• The input source on the transformer is immutable.
• The transformer can be queried to retrieve transformed versions of individual attributes from the source data or the entire data set.

Example

Let's say the following input data is submitted via a POST request to create a new Book.

$input = [
    'title'            => 'a whole new world',
    'price'            => '29.95',
    'publication_date' => '2010-12-09',
    'author'           => 'Jason Daly',
];

Let's also say that we want to be sure the title of the book has been properly titleized, the price is a float value, and the publication date is a Carbon\Carbon datetime object. The attributes of this raw $input can be formatted in a specific, consistent format using a transformer.

use Deefour\Transformer\Transformer;
use Carbon\Carbon;

class BookTransformer extends Transformer
{
    protected $casts [
        'price' => 'float',
    ];

    public function title()
    {
        return trim(ucwords($this->raw('title')));
    }

    public function publicationDate()
    {
        return Carbon::parse($this->raw('publication_date'));
    }
}

The methods are optional, each having public visibility and being named after a camel-cased version of an attribute. These methods will be called whenever those attributes are requested from the transformer.

$transform = new BookTransformer($input);

$transform->get('title');            //=> 'A Whole New World'
$transform->get('price');            //=> 29.95 (cast to a float)
$transform->get('publication_date'); //=> Carbon\Carbon instance

Casts

A protected $casts property can be added to a transformer, composed of attribute names as its keys and the scalar type the attribute should be cast into by the transformer as its values. This mapping will be checked as attributes are returned from a transformer, casting them to the desired type.

class BookTransformer extends Transformer
{
    protected $casts [
        'price' => 'float',
    ];
}

$attributes  = [ 'price' => '3.23' ];
$transformer = new BookTransformer($attributes);

$transformer->price; //=> 3.23 (cast to a float)

Note: Casts to type 'object' and 'array' will be converted to JSON using json_encode.

Hiding Raw Input

A protected $hidden property can be added to a transformer, listing attributes that will be omitted from bulk requests for information like toArray(), all(), and jsonSerialize().

class CarTransformer extends Transformer
{
    protected $hidden = [ 'cylinders' ];
}

$attributes  = [ 'make' => 'Subaru', 'model' => 'WRX', 'cylinders' => 4 ];
$transformer = new Transformer($attributes);

$transformer->cylinders; //=> 4
$transformer->has('cylinders'); //=> true
$transformer->all(); //=> [ 'make' => 'Subaru', 'model' => 'WRX' ]
$transform->except('make'); // [ 'model' => 'WRX' ]

Fallbacks (Default Values)

A protected $fallbacks property can be added to a transformer, composed of attribute names as its keys and default values as its values. This mapping will be checked as attributes are requested from a transformer but cannot be found on the source data or whose value is NULL.

Accepting NULL Values

If an attributes on the source with a NULL value should generally be accepted in favor of a default value in the $fallbacks mapping, this can be enabled for the lifecycle of a request on all transformers by running the following:

Deefour\Transformer\Transformer::preferNullValues();

To illustrate the difference:

class BookTransformer extends Transformer
{
    protected $fallbacks [
        'category' => 'Miscellaneous',
    ];
}


$attributes  = [ 'category' => null ];
$transformer = new BookTransformer($attributes);

$transformer->category; //=> Miscellaneous

Deefour\Transformer\Transformer::preferNullValues();

$transformer->category; //=> null

Method Attributes

Public methods marked with @attribute in their docblock are be treated as attributes on the transformer's $attributes source.

class BookTransformer extends Transformer
{
    /**
     * Is the book considered old?
     *
     * @attribute
     * @return string
     */
    public function isOld()
    {
        return $this->publication_date < Carbon::now()->subYears(10);
    }

    /**
     * Is the book nonfiction?
     *
     * @return boolean
     */
    public function internalSlug()
    {
        return sha1($this->title . (string)$this->publication_date);
    }
}

The isOld method is marked with an @attribute annotation in the docblock, causing the transformer to behave as though an is_old attribute exists on the source data. internalSlug() can be called directly, but it will not be treated as some internal_slug attribute because it has not been marked properly with a docblock annotation.

$transform = new BookTransformer([ 'title' => 'A Whole New World' ]);

$transform->get('title');          //=> 'A Whole New World'
$transform->get('is_old')          //=> false
$transformer->get('internal_slug') //=> null

$transform->all();                 //=> [ 'title' => 'A Whole New World', 'is_old' => false ]

Accessing Data

Individual transformed attributes can be retrieved with get().

$transform->get('title');

A magic __get() implementation provides property access to the transformed attributes

$transform->title;

A magic __call() implementation provides method access

$transformer->title();

The existince of a property can be checked through __isset() or the api

isset($transform->title);

$transform->exists('title');
$transform->has('title');
$transform->contains('title');

Transformers also implement ArrayAccess (attempting to set or unset throws an exception).

$transform['title'];

All transformed attributes can be retrieved at once.

$transform->all();

and a specific set of keys can be plucked all at once.

$transform->only('title', 'price', 'internal_slug'); //=> [ 'title' => 'A Whole New World', 'price' => 29.95, 'internal_slug' => null ]

$transform->intersect('title', 'price', 'internal_slug'); //=> [ 'title' => 'A Whole New World', 'price' => 29.95 ]

$transform->except('secret_key'); //=> everything except the 'secret_key' attribute.
$transform->omit('secret_key');

The JsonSerializable interface is also implemented.

json_encode($transform); //=> "{'title':'A Whole New World', 'price':29.95, 'publication_date':'2010-12-09 00:00:00', 'author':'Jason Daly'}"

Individual raw attributes or the entire raw source can be retrieved.

$transform->raw('title'); //=> 'a whole new world'
$transform->raw(); //=>  [ 'title' => 'a whole new world', 'price' => '29.95', 'publication_date' => '2010-12-09', 'author' => 'Jason Daly' ]

A default value can be provided to get() as a second parameter. If the default is a callable, it will be evaluated before returning.

$transformer->get('invalid-attribute', 'Not Available'); //=> 'Not Available'
$transformer->get('invalid-attribte', function() { return 'Oops!'; }); //=> 'Oops!'

Mutable Transformers

In the base transformer, __set(), offsetSet, and offsetUnset are all null methods. This (lack of) behavior keeps the underlying source data immutable.

A MutableTransformer class exists which does implement these methods, allowing additional properties to be added to, or existing properties to be modified on the transformer instance.

The __call() method can also be used to set/modify attributes on the transformer.

$transformer = new MutableTransformer([ 'foo' => '1234' ]);

$transformer->foo('abcd');

$transformer->get('foo'); //=> 'abcd'

Instantiation and data access are otherwise identical to the base transformer.

Tracking Changes

When an attribute is modified on a mutable transformer, it's original value is maintained. The transformer can be queried to determine if an attribute has been modified after construction or to retrieve a list of changes.

$transformer = new MutableTransformer([ 'foo' => 'AAA', 'bar' => 'BBB' ]);

$transformer->isDirty(); //=> false

$transformer->foo = 'new value';

$transformer->isDirty(); //=> true
$transformer->dirty(); //=> [ 'foo' ]
$transformer->get('foo'); //=> 'new value'
$transformer->original('foo'); //=> 'AAA'

$transformer->changes(); //=> [ 'foo' => 'new value' ]

Contribute

• Issue Tracker: https://github.com/deefour/transformer/issues
• Source Code: https://github.com/deefour/transformer

Changelog

1.7.0 - March 2, 2017

• Added support for hidden attributes from bulk accessors.

1.6.0 - February 14, 2017

• jsonSerialize() will now call jsonSerialize() on attributes implementing JsonSerializable, allowing transformers to recursively be encoded to JSON.

1.5.0 - October 20, 2016

• Rename default() to fallback() throughout the library for compatibility with all PHP versions.

1.4.0 - October 20, 2016

• Support for default attributes being set on a class' new $fallbacks property. This set of defaults will be checked when an attribute is requested which does not exist or is NULL. Thanks to @dgallinari #2

1.3.0 - October 16, 2016

• The @attribute annotation only needs to be set on methods you wish to be treated as attributes that are not camel-cased versions of attributes that exist on the raw input source.
• omit() and without() have been added as aliases for except().
• has() and contains() have been added as aliases for exists().

1.0.1 - October 29, 2015

• Added except() method.

1.0.0 - October 7, 2015

• Release 1.0.0.

0.4.0 - September 7, 2015

• Support added for "attribute methods" - methods who's snake-cased equivalent name is not present in the $attributes source, but who are still treated as any other attribute that is present in the $attributes source.
• protected methods that should not be treated as "attribute methods" should now be tagged @internal in their docblock.

0.3.0 - September 4, 2015

• New change tracking, inspired by yammer/model_attribute

0.2.6 - June 5, 2015

• Now following PSR-2.

0.2.5 - June 3, 2015

• New __call() functionality providing magic method access to attributes.
• get() now handles default values, including closures.

0.2.4 - June 2, 2015

• Fixed bugs in the only() method related to nested attributes.

0.2.2 - May 30, 2015

• raw() will now return the complete, non-transformed source if no $attribute is specified.
• MutableTransformer can now be instantiated without any arguments passed to the constructor.

0.2.1 - May 25, 2015

• Improved code formatting.

0.2.0 - May 5, 2015

• Made the base transformer a regular class (it used to be abstract).
• Added new MutableTransformer.

0.1.0 - April 22, 2015

• Initial release.

License

Copyright (c) 2016 Jason Daly (deefour). Released under the MIT License.