README

An automapper for PHP inspired by .NET's automapper. Transfers data from one object to another, allowing custom mapping operations.

Installation
Why?
Example usage
In depth
Similar libraries
See also
A note on PHPStan
Roadmap

Installation

This library is available on packagist:

$ composer require "mark-gerarts/auto-mapper-plus"

If you're using Symfony, check out the AutoMapper+ bundle.

Why?

When you need to transfer data from one object to another, you'll have to write a lot of boilerplate code. For example when using view models, CommandBus commands, working with API responses, etc.

Automapper+ helps you by automatically transferring properties from one object to another, including private ones. By default, properties with the same name will be transferred. This can be overridden as you like.

Example usage

Suppose you have a class Employee and an associated DTO.

<?php

class Employee
{
    private $id;
    private $firstName;
    private $lastName;
    private $birthYear;
    
    public function __construct($id, $firstName, $lastName, $birthYear)
    {
        $this->id = $id;
        $this->firstName = $firstName;
        $this->lastName = $lastName;
        $this->birthYear = $birthYear;
    }

    public function getId()
    {
        return $this->id;
    }

    // And so on...
}

class EmployeeDto
{
    // While the properties are public for this example, we can map to private
    // or protected properties just the same.
    public $firstName;
    public $lastName;
    public $age;
}

The following snippet provides a quick overview on how the mapper can be configured and used:

<?php

use AutoMapperPlus\Configuration\AutoMapperConfig;
use AutoMapperPlus\AutoMapper;

$config = new AutoMapperConfig();

// Simply registering the mapping is enough to convert properties with the same
// name. Custom actions can be registered for each individual property.
$config
    ->registerMapping(Employee::class, EmployeeDto::class)
    ->forMember('age', function (Employee $source) {
        return date('Y') - $source->getBirthYear();
    })
    ->reverseMap(); // Register the reverse mapping as well.
                            
$mapper = new AutoMapper($config);

// With this configuration we can start converting our objects.
$john = new Employee(10, "John", "Doe", 1980);
$dto = $mapper->map($john, EmployeeDto::class);

echo $dto->firstName; // => "John"
echo $dto->lastName; // => "Doe"
echo $dto->age; // => 37

In depth

Instantiating the AutoMapper

The AutoMapper has to be provided with an AutoMapperConfig, which holds the registered mappings. This can be done in 2 ways:

Passing it to the constructor:

<?php

use AutoMapperPlus\Configuration\AutoMapperConfig;
use AutoMapperPlus\AutoMapper;

$config = new AutoMapperConfig();
$config->registerMapping(Source::class, Destination::class);
$mapper = new AutoMapper($config);

Using the static constructor:

<?php

$mapper = AutoMapper::initialize(function (AutoMapperConfig $config) {
    $config->registerMapping(Source::class, Destination::class);
    $config->registerMapping(AnotherSource::class, Destination::class);
    // ...
});

Using the AutoMapper

Once configured, using the AutoMapper is pretty straightforward:

<?php

$john = new Employee("John", "Doe", 1980);

// Map the source object to a new instance of the destination class.
$mapper->map($john, EmployeeDto::class);

// Mapping to an existing object is possible as well.
$mapper->mapToObject($john, new EmployeeDto());

// Map a collection using mapMultiple
$mapper->mapMultiple($employees, EmployeeDto::class);

Registering mappings

Mappings are defined using the AutoMapperConfig's registerMapping() method. By default, every mapping has to be explicitly defined before you can use it.

A mapping is defined by providing the source class and the destination class. The most basic definition would be as follows:

<?php

$config->registerMapping(Employee::class, EmployeeDto::class);

This will allow objects of the Employee class to be mapped to EmployeeDto instances. Since no extra configuration is provided, the mapping will only transfer properties with the same name.

Custom callbacks

With the forMember() method, you can specify what should happen for the given property of the destination class. When you pass a callback to this method, the return value will be used to set the property.

The callback receives the source object as argument.

<?php

$config->registerMapping(Employee::class, EmployeeDto::class)
    ->forMember('fullName', function (Employee $source) {
        return $source->getFirstName() . ' ' . $source->getLastName();
    });

Operations

Behind the scenes, the callback in the previous example is wrapped in a MapFrom operation. Operations represent the action that should be performed for the given property.

The following operations are provided:

You can use them with the same forMember() method. The Operation class can be used for clarity.

<?php

$getName = function ($source, AutoMapperInterface $mapper) { return 'John'; };

$mapping->forMember('name', $getName);
// The above is a shortcut for the following:
$mapping->forMember('name', Operation::mapFrom($getName));
// Which in turn is equivalent to:
$mapping->forMember('name', new MapFrom($getName));

// Other examples:
// Ignore this property.
$mapping->forMember('id', Operation::ignore());
// Map this property to the given class.
$mapping->forMember('employee', Operation::mapTo(EmployeeDto::class));
// Explicitly state what the property name is of the source object.
$mapping->forMember('name', Operation::fromProperty('unconventially_named_property'));
// The `FromProperty` operation can be chained with `MapTo`, allowing a
// differently named property to be mapped to a class.
$mapping->forMember(
    'address',
    Operation::fromProperty('adres')->mapTo(Address::class)
);
// SetTo sets the property to the given value.
$mapping->forMember('type', Operation::setTo('employee'));

// An extended example showing you can access the mapper in `MapFrom`.
$getColorPalette = function(SimpleXMLElement $XMLElement, AutoMapperInterface $mapper) {
    /** @var SimpleXMLElement $palette */
    $palette = $XMLElement->xpath('/product/specification/palette/colour');
    return $mapper->mapMultiple($palette, Color::class);
};
$mapping->forMember('palette', $getColorPalette);

MapTo requires some extra explanation. Since lists and maps are the same data structure in PHP (arrays), we can't reliably distinct between the two. MapTo therefore accepts a second parameter, $sourceIsObjectArray, a boolean value that indicates whether the source value should be interpreted as a collection, or as an associative array representing an object. By default we assume a collection or a single non-array value.

<?php

// This assumes address is an object, or a collection of mappable
// objects if the source is an array/iterable.
$mapping->forMember('address', Operation::mapTo(Address::class));
// This is equivalent to:
$mapping->forMember('address', Operation::mapTo(Address::class, false));
// If you want to be very specific about the source being a collection, you
// can use `mapCollectionTo`. This is purely syntactic sugar; it is equivalent
// to the declarations above as well.
$mapping->forMember('addresses', Operation::mapCollectionTo(Address::class));

// On the other hand, if the source is an array that represents an object, you
// can use the following:
$mapping->forMember('address', Operation::mapTo(Address::class, true));
// Or nicer
$mapping->forMember('address', Operation::mapArrayTo(Address::class));

You can create your own operations by implementing the MappingOperationInterface. Take a look at the provided implementations for some inspiration.

If you need to have the automapper available in your operation, you can implement the MapperAwareInterface, and use the MapperAwareTrait. The default MapTo and MapFrom operations use these.

Dealing with polymorphic properties

Sometimes you have properties which contain a list of different types of objects e.g. when you load all entities with single table inheritance. You can use MapToAnyOf to map every object to a possible different one. Keep in mind that the mapping for the child class has to be registered as well. The source property can be both a single value or a collection.

<?php

// This iterates over every property of the source property
// 'polymorphicChildren'. Each value will be mapped to the first existing
// mapping from the value to one of the given classes.
$config->createMapping(ChildA::class, ChildADto::class);
$config->createMapping(ChildB::class, ChildBDto::class);
$config->createMapping(Parent::class, ParentDto::class)
    ->forMember(
        'polymorphicChildren',
        Operation::mapToAnyOf([ChildADto::class, ChildBDto::class]
    ));

Dealing with nested mappings

Nested mappings can be registered using the MapTo operation. Keep in mind that the mapping for the child class has to be registered as well.

MapTo supports both single entities and collections.

<?php

$config->registerMapping(Child::class, ChildDto::class);
$config->registerMapping(Parent::class, ParentDto::class)
    ->forMember('child', Operation::mapTo(ChildDto::class));

Handling object construction

You can specify how the new destination object will be constructed (this isn't relevant if you use mapToObject). You can do this by registering a factory callback. This callback will be passed both the source object and an instance of the AutoMapper.

<?php

$config->registerMapping(Source::class, Destination::class)
    ->beConstructedUsing(function (Source $source, AutoMapperInterface $mapper): Destination {
        return new Destination($source->getProperty());
    });

Another option is to skip the constructor all together. This can be set using the options.

<?php

// Either set it in the options:
$config->getOptions()->skipConstructor();
$mapper = new AutoMapper($config);

// Or set it on the mapping directly:
$config->registerMapping(Source::class, Destination::class)->skipConstructor();

ReverseMap

Since it is a common use case to map in both directions, the reverseMap() method has been provided. This creates a new mapping in the alternate direction.

reverseMap will keep the registered naming conventions into account, if there are any.

<?php

// reverseMap() returns the new mapping, allowing to continue configuring the
// new mapping.
$config->registerMapping(Employee::class, EmployeeDto::class)
    ->reverseMap()
    ->forMember('id', Operation::ignore());

$config->hasMappingFor(Employee::class, EmployeeDto::class); // => True
$config->hasMappingFor(EmployeeDto::class, Employee::class); // => True

Note: reverseMap() simply creates a completely new mapping in the reverse direction, using the default options. However, every operation you defined with forMember that implements the Reversible interface, gets defined for the new mapping as well. Currently, only fromProperty supports being reversed.

To make things more clear, take a look at the following example:

<?php

// Source class properties:         Destination class properties:
// - 'some_property',               - 'some_property'
// - 'some_alternative_property'    - 'some_other_property'
// - 'the_last_property'            - 'the_last_property'
//
$config->registerMapping(Source::class, Destination::class)
    ->forMember('some_property', Operation::ignore())
    ->forMember('some_other_property', Operation::fromProperty('some_alternative_property'))
    ->reverseMap();

// When mapping from Source to Destination, the following will happen:
// - some_property gets ignored
// - some_other_property gets mapped by using the value form some_alternative_property
// - the_last_property gets mapped because the names are equal.
//
// Now, when we go in the reverse direction things are different:
// - some_property gets mapped, because Ignore is not reversible
// - some_alternative_property gets mapped because FromProperty is reversible
// - the_last_property gets mapped as well

Copying a mapping

When defining different view models, it can occur that you have lots of similar properties. For example, with a ListViewModel and a DetailViewModel. This means that the mapping configuration will be similar as well.

For this reason, it is possible to copy a mapping. In practice this means that all the options will be copied, and all the explicitly defined mapping operations.

After copying the mapping, you're free to override operations or options on the new mapping.

<?php

$detailMapping = $config->registerMapping(Employee::class, EmployeeDetailView::class)
    // Define operations and options ...
    ->forMember('age', function () {
        return 20;
    });

// You can copy a mapping by passing source and destination class. This will
// search the config for the relevant mapping.
$listMapping = $config->registerMapping(Employee::class, EmployeeListView::class)
    ->copyFrom(Employee::class, EmployeeDetailView::class)
    // Alternatively, copy a mapping by passing it directly.
    // ->copyFromMapping($detailMapping)
    //
    // You can now go ahead and define new operations, or override existing
    // ones.
    ->forMember('name', Operation::ignore())
    ->skipConstructor();

Automatic creation of mappings

When you're dealing with very simple mappings that don't require any configuration, it can be quite cumbersome the register a mapping for each and every mapping. For these cases it is possible to enable the automatic creation of mappings:

<?php

$config->getOptions()->createUnregisteredMappings();

With this configuration the mapper will generate a very basic mapping on the fly instead of throwing an exception if the mapping is not configured.

Resolving property names

Unless you define a specific way to fetch a value (e.g. mapFrom), the mapper has to have a way to know which source property to map from. By default, it will try to transfer data between properties of the same name. There are, however, a few ways to alter this behaviour.

If a source property is specifically defined (e.g. FromProperty), this will be used in all cases.

Naming conventions

You can specify the naming conventions followed by the source & destination classes. The mapper will take this into account when resolving names.

For example:

<?php

use AutoMapperPlus\NameConverter\NamingConvention\CamelCaseNamingConvention;
use AutoMapperPlus\NameConverter\NamingConvention\SnakeCaseNamingConvention;

$config->registerMapping(CamelCaseSource::class, SnakeCaseDestination::class)
    ->withNamingConventions(
        new CamelCaseNamingConvention(), // The naming convention of the source class.
        new SnakeCaseNamingConvention() // The naming convention of the destination class.
    );

$source = new CamelCaseSource();
$source->propertyName = 'camel';

$result = $mapper->map($source, SnakeCaseDestination::class);
echo $result->property_name; // => "camel"

The following conventions are provided (more to come):

CamelCaseNamingConvention
PascalCaseNamingConvention
SnakeCaseNamingConvention

You can implement your own by using the NamingConventionInterface.

Explicitly state source property

As mentioned earlier, the operation FromProperty allows you to explicitly state what property of the source object should be used.

<?php

$config->registerMapping(Source::class, Destination::class)
    ->forMember('id', Operation::fromProperty('identifier'));

You should read the previous snippet as follows: "For the property named 'id' on the destination object, use the value of the 'identifier' property of the source object".

FromProperty is Reversible, meaning that when you apply reverseMap(), AutoMapper will know how to map between the two properties. For more info, read the section about reverseMap.

Resolving names with a callback

Should naming conventions and explicitly stating property names not be sufficient, you can resort to a CallbackNameResolver (or implement your own NameResolverInterface).

This CallbackNameResolver takes a callback as an argument, and will use this to transform property names.

<?php

class Uppercase
{
    public $IMAPROPERTY;
}

class Lowercase
{
    public $imaproperty;
}

$uppercaseResolver = new CallbackNameResolver(function ($targetProperty) {
    return strtolower($targetProperty);
});

$config->registerMapping(Uppercase::class; Lowercase::class)
    ->withNameResolver($uppercaseResolver);

$uc = new Uppercase();
$uc->IMAPROPERTY = 'value';

$lc = $mapper->map($uc, Lowercase::class);
echo $lc->imaproperty; // => "value"

The Options object

The Options object is a value object containing the possible options for both the AutoMapperConfig and the Mapping instances.

The Options you set for the AutoMapperConfig will act as the default options for every Mapping you register. These options can be overridden for every mapping.

For example:

<?php

$config = new AutoMapperConfig();
$config->getOptions()->setDefaultMappingOperation(Operation::ignore());

$defaultMapping = $config->registerMapping(Source::class, Destination::class);
$overriddenMapping = $config->registerMapping(AnotherSource::class, Destination::class)
    ->withDefaultOperation(new DefaultMappingOperation());

$defaultMapping->getOptions()->getDefaultMappingOperation(); // => Ignore
$overriddenMapping->getOptions()->getDefaultMappingOperation(); // => DefaultMappingOperation

The available options that can be set are:

Setting the options

For the AutoMapperConfig

You can set the options for the AutoMapperConfig by retrieving the object:

<?php

$config = new AutoMapperConfig();
$config->getOptions()->dontSkipConstructor();

Alternatively, you can set the options by providing a callback to the constructor. The callback will be passed an instance of the default Options:

<?php

// This will set the options for this specific mapping.
$config = new AutoMapperConfig(function (Options $options) {
    $options->dontSkipConstructor();
    $options->setDefaultMappingOperation(Operation::ignore());
    // ...
});

For the Mappings

A mapping also has the getOptions method available. However, chainable helper methods exist for more convenient overriding of the options:

<?php

$config->registerMapping(Source::class, Destination::class)
    ->skipConstructor()
    ->withDefaultOperation(Operation::ignore());

Setting options via a callable has been provided for mappings as well, using the setDefaults() method:

<?php

$config->registerMapping(Source::class, Destination::class)
    ->setDefaults(function (Options $options) {
        $options->dontSkipConstructor();
        // ...
    });

Mapping with stdClass

As a side note it is worth mentioning that it is possible to map from and to stdClass. Mapping from stdClass happens as you would expect, copying properties to the new object.

<?php

// Register the mapping.
$config->registerMapping(\stdClass::class, Employee::class);
$mapper = new AutoMapper($config);

$employee = new \stdClass();
$employee->firstName = 'John';
$employee->lastName = 'Doe';

$result = $mapper->map($employee, Employee::class);
echo $result->firstName; // => "John"
echo $result->lastName; // => "Doe"

Mapping to \stdClass requires some explanation. All properties available on the provided source object are copied to the \stdClass as public properties. It's still possible to define operations for individual properties (for example, to ignore a property).

<?php

// Operations can still be registered.
$config->registerMapping(Employee::class, \stdClass::class)
    ->forMember('id', Operation::ignore());
$mapper = new AutoMapper($config);

$employee = new Employee(5, 'John', 'Doe', 1978);
$result = $mapper->map($employee, \stdClass::class);

echo $result->firstName; // => "John"
echo $result->lastName; // => "Doe"
var_dump(isset($result->id)); // => bool(false)

Naming conventions will be taken into account, so keep this in mind when defining operations. The property name has to match the naming convention of the target.

<?php

$config->registerMapping(CamelCaseSource::class, \stdClass::class)
    ->withNamingConventions(
        new CamelCaseNamingConvention(),
        new SnakeCaseNamingConvention()
    )
    // Operations have to be defined using the target property name.
    ->forMember('some_property', function () { return 'new value'; });
$mapper = new AutoMapper($config);

$source = new CamelCaseSource();
$source->someProperty = 'original value';
$source->anotherProperty = 'Another value';
$result = $mapper->map($employee, \stdClass::class);

var_dump(isset($result->someProperty)); // => bool(false)
echo $result->some_property; // => "new value"
echo $result->another_property; // => "Another value"

The concept of object crates

As suggested and explained in this issue, AutoMapper+ uses object crates to allow mapping to \stdClass. This means you can register your own classes as well to be an object crate. This makes the mapper handle it exactly as \stdClass, writing all source properties to public properties on the target.

Registering object crates can be done using the Options.

<?php

class YourObjectCrate { }

$config = new AutoMapperConfig(); // (Or pass a callable to the constructor)
$config->getOptions()->registerObjectCrate(YourObjectCrate::class);
$config->registerMapping(Employee::class, YourObjectCrate::class);
$mapper = new AutoMapper($config);

$employee = new Employee(5, 'John', 'Doe', 1978);
$result = $mapper->map($employee, YourObjectCrate::class);

echo $result->firstName; // => "John"
echo $result->lastName; // => "Doe"
echo get_class($result); // => "YourObjectCrate"

Mapping with arrays

It is possible to map associative arrays into objects (shout-out to @slava-v). This can be done just like you would declare a regular mapping:

<?php

$config->registerMapping('array', Employee::class); // Alternatively, use the enum DataType::ARRAY
// Adding operations works just as you would expect.
$config->registerMapping(DataType::ARRAY, Employee::class)
    ->forMember('id', Operation::ignore())
    ->forMember('type', Operation::setTo('employee'))
    // Since arrays are oftentimes snake_case'd.
    ->withNamingConventions(
        new SnakeCaseNamingConvention(),
        new CamelCaseNamingConvention()
    );

// It is now possible to map an array to an employee:
$employee = [
    'id' => 5,
    'first_name' => 'John',
    'last_name' => 'Doe'
];
$result = $mapper->map($employee, Employee::class);
echo $result->firstName; // => "John"
echo $result->id; // => null
echo $result->type; // => "employee"

See the MapTo section under Operations for some more details about the intricacies involving this operation in combination with arrays.

As for now, it is not possible to map to an array. While this is relatively easy to implement, it would introduce a breaking change. It is part of version 2.x, so check there if you need this feature.

Using a custom mapper

This library attempts to make registering mappings painless, with as little configuration as possible. However, cases exist where a mapping requires a lot of custom code. This code would look a lot cleaner if put in its own class. Another reason to resort to a custom mapper would be performance.

It is therefore possible to specify a custom mapper class for a mapping. This mapper has to implement the MapperInterface. For your convenience, a CustomMapper class has been provided that implements this interface.

<?php

// You can either extend the CustomMapper, or just implement the MapperInterface
// directly.
class EmployeeMapper extends CustomMapper
{
    /**
     * @param Employee $source
     * @param EmployeeDto $destination
     * @return EmployeeDto
     */
    public function mapToObject($source, $destination)
    {
        $destination->id = $source->getId();
        $destination->firstName = $source->getFirstName();
        $destination->lastName = $source->getLastName();
        $destination->age = date('Y') - $source->getBirthYear();

        return $destination;
    }
}

$config->registerMapping(Employee::class, EmployeeDto::class)
    ->useCustomMapper(new EmployeeMapper());
$mapper = new AutoMapper($config);

// The AutoMapper can now be used as usual, but your custom mapper class will be
// called to do the actual mapping.
$employee = new Employee(10, 'John', 'Doe', 1980);
$result = $mapper->map($employee, EmployeeDto::class);

Adding context

Sometimes a mapping should behave differently based on the context. It is therefore possible to pass a third argument to the map methods to describe the current context. Both the MapFrom and MapTo operations can make use of this context to alter their behaviour.

The context argument is an array that can contain any arbitrary value. Note that this argument isn't part of the AutoMapperInterface yet, since it would break backwards compatibility. It will be added in the next major release.

<?php

// This example shows how for example the current locale can be passed to alter
// the mapping behaviour.
$config->registerMapping(Employee::class, EmployeeDto::class)
    ->forMember(
        'honorific',
        function ($source, AutoMapperInterface $mapper, array $context): string {
            $translationKey = "honorific.{$source->getGender()}";
            return $this->translator->trans($translationKey, $context['locale']);
        }
    );

// Usage:
$mapper->map($employee, EmployeeDto::class, ['locale' => $request->getLocale()]);

When using the mapToObject method, the context will contain the destination object by default. It is accessible using $context[AutoMapper::DESTINATION_CONTEXT]. This is useful in scenarios where you need data from the destination object to populate the object you're mapping.

When implementing a custom constructor, the context will contain the destination class by default. It is accessible using $context[AutoMapper::DESTINATION_CLASS_CONTEXT].

When mapping an object graph, the context will also contain arrays for property name paths, ancestor source objects and ancestor destination objects. Those arrays are accessible using $context[AutoMapper::PROPERTY_STACK_CONTEXT], $context[AutoMapper::SOURCE_STACK_CONTEXT] and $context[AutoMapper::DESTINATION_STACK_CONTEXT]. They can be used to implement custom mapping function based on the hierarchy level and current position inside the object graph being mapped.

Misc

Passing NULL as an argument for the source object to map returns NULL.

Similar libraries

When picking a library, it's important to see what options are available. No library is perfect, and they all have their pro's and con's.

A few other object mappers exist for PHP. They're listed here with a short description, and are definitely worth checking out!

Jane automapper:
- Similar API
- Compiles mappings, resulting in near-native performance
Nylle/PHP-AutoMapper:
- Only maps public properties
- Requires some conventions to be met
- Does some interesting stuff with types
Papper:
- Convention based
- High performance
- Lacks in documentation
BCCAutoMapperBundle:
- Only available as a Symfony bundle (<3.0)
- Very similar to this project
- Does some cool stuff with graph mapping

Performance benchmarks (credit goes to idr0id):

Runtime: PHP 7.2.9-1
Host: Linux 4.18.0-2-amd64 #1 SMP Debian 4.18.10-2 (2018-11-02) x86_64
Collection size: 100000

Up-to-date benchmarks can be found here.

Note that using a custom mapper is very fast. So when performance really starts to matter in your application, you can easily implement a custom mapper where needed, without needing to change the code that uses the mapper.

A note on PHPStan

Because of an issue described here, PHPStan reports the following error if you use the $context parameter:

Method AutoMapperPlus\MapperInterface::map() invoked with 3 parameters, 2 required.

If you see this error, you should enable the AutoMapper+ extension. Please note that this is a temporary solution. The issue will be fixed in the 2.0 release.

Roadmap

Provide a more detailed tutorial
Create a sample app demonstrating the automapper
Allow mapping from stdClass,
or perhaps even an associative array (could have)
Allow mapping to stdClass
Provide options to copy a mapping
Allow setting of prefix for name resolver (see automapper)
Create operation to copy value from property
Allow passing of contructor function
Allow configuring of options in AutoMapperConfig -> error when trying with a registered mapping
Consider: passing of options to a single mapping operation
MapTo: allow mapping of collection
Clean up the property checking in the Mapping::forMember() method.
Refactor tests
Allow setting a maximum depth, see #14
Provide a NameResolver that accepts an array mapping, as an alternative to multiple FromPropertys
Make use of a decorated Symfony's PropertyAccessor (see #16)
Allow adding of middleware to the mapper
Allow mapping to array

Version 2 is in the works, check there for new features as well

mark-gerarts / auto-mapper-plus

Maintainers

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