packagefactory/extractor

A fluent interface that allows to validate primitive PHP data structures while also reading them

v1.0.2 2022-12-17 14:28 UTC

Requires

• php: >=8.1

Requires (Dev)

• phpstan/phpstan: ^1.9
• phpunit/phpunit: ^9.5
• squizlabs/php_codesniffer: ^3.7

GPL-3.0-or-later

README

A fluent interface that allows to validate primitive PHP data structures while also reading them

Installation

composer require --dev packagefactory/extractor

Usage

Let's say, you have a PHP-native array structure like this one:

$configuration = [
    'mailer' => [
        'transport' => 'smtp',
        'host' => 'smtp.example.com',
        'port' => 465
    ]
];

It contains configuration for a mailing service. In a lot of PHP projects, configuration comes in this format, usually by being parsed from YAML or JSON sources. While these formats are nicely readable and writable, the result PHP array data structure is completely exempt from type safety.

It is much more desirable to handle the given configuration using a value object like this one:

final class MailerConfiguration
{
    private function __construct(
        public readonly MailerTransport $transport,
        public readonly string $host,
        public readonly int $port
    ) {
    }
}

To convert the array structure into this object, it may be suitable to write a static factory method:

final class MailerConfiguration
{
    /* ... */

    public static function fromArray(array $array): self
    {
        if (!isset($array['transport']) || !is_string($array['transport'])) {
            throw new \Exception('Transport must be a string!');
        }

        if (!isset($array['host']) || !is_string($array['host'])) {
            throw new \Exception('Host must be a string!');
        }

        if (!isset($array['port']) || !is_int($array['port'])) {
            throw new \Exception('Port must be an integer!');
        }

        return new self(
            transport: MailerTransport::from($array['transport']),
            host: $array['host'],
            port: $array['port']
        );
    }
}

Unfortunately, this is a lot of code to write and it would become even more, if we'd actually like to have more helpful error messages.

This is where the Extractor comes in. Using the Extractor API, we can write a static factory method like this:

final class MailerConfiguration
{
    /* ... */

    public static function fromExtractor(Extractor $extractor): self
    {
        return new self(
            transport: MailerTransport::from($extractor['transport']->string()),
            host: $extractor['host']->string(),
            port: $extractor['port']->int()
        );
    }
}

The extractor handles the runtime type checks for us and throws helpful error messages, if the datastructure doesn't follow our assumptions.

To complete the example from the beginning:

$configuration = [
    'mailer' => [
        'transport' => 'smtp',
        'host' => 'smtp.example.com',
        'port' => 465
    ]
];

$mailerConfiguration = MailerConfiguration::fromExtractor(
    Extractor::for($configuration)['mailer']
);

API

Type Guards

bool and boolOrNull

Extractor::for(true)->bool(); // returns `true`
Extractor::for(false)->bool(); // returns `false`
Extractor::for(true)->boolOrNull(); // returns `true`
Extractor::for(false)->boolOrNull(); // returns `false`
Extractor::for(null)->boolOrNull(); // returns `null`

Checks if the data given to the extractor is a boolean and returns it if thats the case. When boolOrNull is used, null will pass as well.

int and intOrNull

Extractor::for(42)->int(); // returns `42`
Extractor::for(42)->intOrNull(); // returns `42`
Extractor::for(null)->intOrNull(); // returns `null`

Checks if the data given to the extractor is an integer and returns it if thats the case. When intOrNull is used, null will pass as well.

float and floatOrNull

Extractor::for(47.11)->float(); // returns `47.11`
Extractor::for(47.11)->floatOrNull(); // returns `47.11`
Extractor::for(null)->floatOrNull(); // returns `null`

Checks if the data given to the extractor is a float and returns it if thats the case. When floatOrNull is used, null will pass as well.

intOrFloat and intOrFloatOrNull

Extractor::for(42)->intOrFloat(); // returns `42`
Extractor::for(47.11)->intOrFloat(); // returns `47.11`
Extractor::for(42)->intOrfloatOrNull(); // returns `42`
Extractor::for(47.11)->intOrfloatOrNull(); // returns `47.11`
Extractor::for(null)->intOrfloatOrNull(); // returns `null`

In JSON there's no distinction between integer and float types. Everything is just a number. These two methods check if the data given to the extractor is a float or an integer (and therefore a number) and returns it if thats the case. When intOrfloatOrNull is used, null will pass as well.

string and stringOrNull

Extractor::for('string')->string(); // returns `"string"`
Extractor::for('string')->stringOrNull(); // returns `"string"`
Extractor::for(null)->stringOrNull(); // returns `null`

Checks if the data given to the extractor is a string and returns it if thats the case. When stringOrNull is used, null will pass as well.

array and arrayOrNull

Extractor::for([])->array(); // returns `[]`
Extractor::for([])->arrayOrNull(); // returns `[]`
Extractor::for(null)->arrayOrNull(); // returns `null`

Checks if the data given to the extractor is an array and returns it if thats the case. When stringOrNull is used, null will pass as well.

Array Access

In order to deal with nested array structures, Extractor implements the \ArrayAccess interface.

Given you have an Extractor that wraps an array, when you access a key, you'll receive the value for that key wrapped in another Extractor instance:

$extractor = Extractor::for([ 'key' => 'value' ]);
$extractor['key']->string(); // returns `"value"`
$extractor['key']->int(); // throws

If you access an unknown key, it'll be treated like Extractor::for(null):

$extractor['unknown key']->stringOrNull(); // returns `null`
$extractor['unknown key']->string(); // throws

If you access a key on something other than an array, Extractor will throw:

$extractor = Extractor::for('This is not an array...');
$extractor['key']; // throws

getPath

Each Extractor instance provides you with the access path by which it has been retrieved:

$extractor = Extractor::for([ 
    'some' => [
        'deep' => [
            'path' => '1234'
        ]
    ]
]);

$nested = $extractor['some']['deep']['path'];
var_dump($nested->getPath());
// Output:
// array(3) {
//   [0] =>
//   string(4) "some"
//   [1] =>
//   string(4) "deep"
//   [2] =>
//   string(4) "path"
// }

Iterable

Extractor implements the \IterableAggregate interface, which allows you to loop over it using foreach:

foreach (Extractor::for([ 'key' => 'value' ]) as $key => $value) {
    $key->string(); // returns `"key"`
    $value->string(); // returns `"value"`

    $key->int(); // throws
}

As you see, both $key and $value are themselves instances of Extractor.

If you try to iterate over an Extractor that wraps something other than an array, the Extractor will throw:

foreach (Extractor::for('This is not an array...') as $key => $value) { // throws
}

Error Handling

Extractor may throw instances of ExtractorException. Each ExtractorException carries the access path by which the throwing Extractor has been retrieved and tries to provide a helpful error message:

$extractor = Extractor::for([ 
    'some' => [
        'deep' => [
            'path' => '1234'
        ]
    ]
]);

try {
    $extractor['some']['deep']['path']->int();
} catch (ExtractorException $e) {
    var_dump($e->getPath());
    // Output:
    // array(3) {
    //   [0] =>
    //   string(4) "some"
    //   [1] =>
    //   string(4) "deep"
    //   [2] =>
    //   string(4) "path"
    // }

    var_dump($e->getMessage()); 
    // Output:
    // string(65) "Value was expected to be of type int, got string("1234") instead."
}

Contribution

We will gladly accept contributions. Please send us pull requests.

License

see LICENSE