Laravel Transformer
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README.md

Laravel Scene

Laravel library to convert your models into API responses.

Why a transformation library?

By default you can use the default implementation which converts your models to json based on toArray(). This approach starts to get messy once you start having different responses for your models for different endpoints (Eg: based on user permissions, endpoint types, etc).

This library also allows you to seperate your object transformation logic from your Models. Your models do not need to concern themselves with how they get represented over the wire at different endpoints. The same way you can use the transformers to transform objects or arrays. They don't have to be eloquent models.

Note: Laravel API Resource is a great start if you're using >= 5.5. In that case you should carefully evaluate your needs and how your complexity will grow before choosing this.

Installation

Install using composer.

composer require azaan/laravel-scene

Usage

Create a transformer class to transform your model. You can use the same transform method to transform an array/collection of objects or a single object.

Example.

class PersonTransformer extends SceneTransformer {
    
    /**
     * Eloquent relations to preload
     *
     * Note: It will only get preloaded if it already isnt.
     */
    protected function getPreloadRelations()
    {
        return [
            // preload nested relations of posts defined in PostTransformer
            'posts'   => SceneTransformer::PRELOAD_RELATED,
            
            // load addresses if $this->showMin is truthy
            'address' => $this->showMin,
            
            // preload createdBy relation
            'createdBy',
        ];
    }

    /**
     * Structure transformations.
     *
     * @return array structure
     */
    protected function getStructure()
    {
        return [
            'id',
            'name',
            'email',
            'fullname',
            'actions',
            'address' => [
                'name',
                'street',
            ],
            'status' => new ArrayMapTransform([
                'active'        => 'Active',
                'blocked'       => 'Blocked',
                'temp-disabled' => 'Temporarily Disabled',
            ]),
            'posts' => PostTransformer::createMinTransformer(),
            
            // return the field 'joined_date' as 'date',
            'date' => 'joined_date',
            
            'created_at' => new DateFormatTransform('Y-m-d'),
        ];
    }
    
    /**
     * Structure to use when returning multiple objects
     *
     * @return array structure
     */
    protected function getMinStructure()
    {
        return [
            'id',
            'name',
            'email',
            
            // add extra key only when some condition meets
            'extra' => $this->when($this->someCondition, 'extra'),
        ];
    }

    protected function getFullname(Person $person)
    {
        return $person->first_name . ' ' . $person->last_name;
    }
    
    protected function getActions(Person $person)
    {
        // call service methods to figure out what actions the user can perform
        
        return ['can_edit', 'can_update'];
    }
}

Now in your controller method.

    public function all()
    {
        $people = $this->personService->getAllPeople();

        $transformer = PersonTransformer::createMinTransformer();
        return SceneResponse::respond($people, $transformer);
    }
    
    public function show($id)
    {
        $person = $this->personService->getPersonByIdOrFail($id);
        
        $transformer = new PersonTransformer();
        return SceneResponse::respond($person, $transformer);
    }

You can use the SceneRespond::respond method with either a collection of data or a single object. The transformer will handle it appropriately. It can also handle a LengthAwarePaginator.

In this example it is assumed your model (Person) has the attributes id, name, email and created_at. For the field fullname the method getFullname is used to resolve the value.

Keys are resolved using the following steps:

  1. If a getter method exists in the transformer it is called
  2. Check if the key exists on the object
  3. Check if a getter method for the key exists on the object
  4. Returns null

Nesting Transformers

You can nest transformers within another transformer. For example if you had a Company model with a relation called owner which resolves to a Person object your Company transformer can look like this.

class CompanyTransformer extends SceneTransformer {
    /**
     * Structure transformations.
     *
     * @return array structure
     */
    protected function getStructure()
    {
        return [
            'id',
            'name',
            'owner' => new PersonTransformer()
        ];
    }
}

This way your transform logic for every model is compartmentalised and can easily be reused.

Hooks

Several hook methods are defined which you can override to get desired behaviour.

Injecting from Laravel Container

If you need to inject classes from the laravel container you can override the method inject. All parameters of the inject method will be resolved from the Laravel Container.

Minimum Structure

When you're responding with a collection of objects (Eg: for a listing) you might want to respond with different fields. You can use this by overriding the method getMinStructure(). In this case when you're instantiating the transformer in the controller use the method ::createMinTransformer()

Preload Eloquent relations

When responding with a collection of eloquent objects and accessing relations which haven't been loaded it will lead to the N+1 query problem. You can override the method getPreloadRelations and return an array of relations to be preloaded by the transformer. The transformer will take care of only loading the relations which haven't been loaded and will load them whenever appropriate. You can also use dot notation to preload nested relations. (Eg: person.address)

Pre process

Override the methods preProcessSingle and preProcessCollection to run any pre process logic before the transformer starts transforming the objects.

Null State

Override the method getNullState to return the default state if the object is null. Default implementation returns null

Ordering

Usually it is better to do your ordering before passing into the transformer. However in cases where you require to order by a field which is only present after the transformation you can override getOrderBy to provide ordering. You should return the field name as a string to order by. If you require direction return an array. (Eg: ['field_name', 'DESC'])

Post process hook.

To do any changes after all transformations you can override the method transformObject. The transformed output array will be passed in as the first argument and original object as the second.

Licence

MIT