Transformer part of Quibble

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Latest release

0.1.0

Date: github

README.md

Transformers for query result( sets)

Easily cast and transform a single result set or a collection of results from a database query.

Installation

$ cd /path/to/your/project
$ composer require quibble/transformer

Usage

Instantiate a transformer and either call the collection or resource method. The first parameter is the query result, the second a callable used to determine how to transform the result(s):

<?php

use Quibble\Transformer\Transformer;

$transformer = new Transformer;

$results = $statement->fetchAll();
$results = $transformer->collection($results, function () {});

$result = $statement->fetch();
$result = $transformer->resource($result, function () {});

Internally, collection is simply a convenient front to array_map(Transformer::resource). In all other respects they work identically. The rest of this README will therefore only use resource.

The default behaviour is to remove all numeric keys from resources as if one had fetched it using PDO::FETCH_ASSOC. To override this you may instantiate the transformer with a false parameter.

You can only transform results returned as an array. The assumption is that if you fetch "into" objects (models) these would do their own massaging. You will however see later on how we can transform into objects as well.

Defining a transformation

The key to specifying the transformation is to type hint the named parameters you want to have transformed. By default PDO returns most things as strings. We can simply specify a few fields we want to be cast:

<?php

$result = $transformer->resource($result, function (int $id, bool $active) {});

We can also type hint any object. The assumption is that such an object will be instantiated with the original value as its first and only argument. E.g.:

<?php

use Carbon\Carbon;

$result = $transformer->resource($result, function (Carbon $datecreated) {});

Any fields not specifically transformed are passed verbatim, and any fields mentioned in the transformed not present in the result are simply ignored. The idea is that you specify transformers with all transformable fields for a table, but your query doesn't necessarily do "SELECT *". This way you can easily reuse transformers.

Modifying the return type

PHP7+ allows us to type-hint a return type. If a transformer does this, an object of that type (or an array of them, in the case of collection) is returned instead:

<?php

$result = $transformer->resource($result, function () : stdClass {});
$result typeof stdClass; // true

Specifying multiple transformers

More than one transformer may be given; just add additional arguments. They are applied in order and if more than one specifies a return type, only the last is used. This allows you to quickly specify overrides for certain query results. If a field would be transformed twice using this method, it is first cast back to a string before being passed to the next transformer. If you instead would like to pass the transformed value (because your decorator uses type hinting in its constructor itself) specify it with a default null value.

Centralizing your code (DRY)

Instead of manually passing lambdas around, a much cleaner pattern would be to specify your transformers as class methods. You might do this on a model, or in a central interface. Remember, we're not actually calling these methods, we just want to inspect them!

<?php

use Carbon\Carbon;

interface MySchema
{
    public function foo(int $id, Carbon $datecreated) : MyAwesomeModel;
    // A return type of array is actually the default.
    public function bar(int $id, bool $valid) : array;
}

$fooResult = $transformer->resource($fooResult, [MySchema::class, 'foo']);
$barResult = $transformer->resource($barResult, [MySchema::class, 'bar']);

FAQ

Do I need any other Quibble module to use this?

Nope. You don't even need PDO as long as you're dealing with arrays.